Mega IPOs: What do they mean for investors?

What the next wave of IPOs could mean for investments.

SpaceX, OpenAI, and Anthropic are among the largest private companies in the world, and all three are now widely discussed as potential candidates for an IPO in the next eighteen months. Depending on the reported valuations that are used, they would together represent about $3,250 to $3,750 billion in value on the private markets.

For long-term investors, however, the most important question is usually not whether to buy these shares on the first day of trading. Rather, it is a question of determining whether their arrival on the public markets changes the value, risk or behaviour of the assets already in the portfolio. In many cases, this is indeed the case.

What makes an IPO a “mega-IPO”

An IPO is simply when a private company begins to be listed on a public market. A mega-IPO is the same event, but on a completely different scale: a listing large enough to :

• absorb significant institutional capital,
• attract considerable media attention,
• and influence the valuation of comparable listed companies.

Large IPOs can redirect capital flows, reshape sector valuations, and create expectations of future purchases by indices. In other words, these are not just company-specific events. These are market events. When the companies concerned reach such a size, investors do not need to buy them directly to feel the effects. They may already have exposure to it via suppliers, strategic investors, index funds or adjacent positions in the same field.

The three names at the heart of the discussion

SpaceX

According to published information, SpaceX confidentially filed an IPO file in early April and could target a valuation of around $1,750 to $2,000 billion with the start of trading in June on the Nasdaq under the symbol “SPCX”. A potential raise of $75 billion (3x Saudi Aramco’s record in 2019) is planned with an important allocation of the shares for retail investors, a proportion that is nevertheless unusual.

What sets SpaceX apart from the typical IPO candidate is that it’s not just a story based on future demand. It is already a large operational company, with Starlink as an important commercial driver in addition to the rocket launch business. This makes future public valuation particularly important for investors who already own aerospace, defense, satellite, or infrastructure companies. If the market gives SpaceX an exceptionally high valuation, it could support comparable companies. Conversely, a disappointment could weigh on this whole.

OpenAI

OpenAI, the company behind ChatGPT, announced on March 31 that it had closed a $122 billion fundraising round at a post-money valuation of $852 billion (the value of a company after it has received an investment), while indicating that it now generates $2 billion in revenue per month. The company has still not officially filed for an IPO, but the signals are accelerating. The Wall Street Journal reported that the company is laying the groundwork for a potential IPO in the fourth quarter of 2026, with a target valuation of up to $1 trillion.

The stakes go beyond OpenAI itself. Part of its value is already reflected in listed companies linked to its financing, such as Amazon, Nvidia, SoftBank and especially Microsoft. For investors with exposure to these securities or diversified technology funds, a potential IPO would not create new exposure: it would simply give a more explicit market price to an already existing exposure.

Anthropic

Anthropic, the creator of Claude, raised $30 billion in February at a post-money valuation of $380 billion, at which point the company said it had an annualized revenue rate of $14 billion. Growth then accelerated sharply. By April 2026, Anthropic’s annualized pace had surpassed $30 billion, surpassing OpenAI, and SemiAnalysis reported that it had reached $44 billion in May, at a rate that would roughly double every six weeks. The company is now reportedly in talks to raise an additional $30 billion at a valuation of around $900 billion ahead of a possible IPO.

This combination of rapid growth and high valuation in private markets has made Anthropic a central player in the broader AI valuation debate. Even before any formal IPO filing, its valuation helps set expectations for listed companies in software, cloud infrastructure, semiconductors, and enterprise AI. Investors do not need to own Anthropic shares to be affected by how the market thinks Anthropic should be valued. The contagion effect can affect the entire AI ecosystem.

Why these introductions could affect existing portfolios

• The first reason is indirect exposure. If you own large technology companies, diversified equity funds or AI-related thematic positions, you may already have economic exposure to these companies via strategic investments, business relationships or valuation effects by comparison. An IPO does not necessarily introduce something new to the portfolio. Often, it simply makes what was already integrated into it more visible.
• The second reason is liquidity. Very large operations do not make capital appear out of nothing. Institutions that want to secure significant allocations in a mega-IPO often fund these purchases by reducing related positions. This can create temporary weakness in adjacent stocks, especially in the same sector or theme. Investors sometimes interpret this weakness as a change in fundamentals, when in reality it is a capital turnover.
• The third reason is the benchmark effect. Many investors assume that a high-profile IPO quickly enters the major indices and then benefits from mechanical purchases by passive funds. It can happen, but it’s not automatic. Under current rules, profitability and seniority requirements have traditionally limited rapid inclusion in the S&P 500. In late April, S&P Dow Jones Indices opened a consultation on possible rule changes that could shorten the waiting period for large newly listed companies and potentially remove profitability requirements for ultra-large-cap entrants. If adopted, these changes could significantly affect the timing and magnitude of passive demand. This is important because investors often incorporate inclusion into indices before it actually happens. Expectations alone can move prices. If these expectations turn out to be too optimistic, the reversal can be just as abrupt.

Are we facing a new “dot-com” moment?

The comparison is legitimate, but it must be made with caution.

The wave of IPOs in the late 1990s was exceptional, both in terms of its volume and the speculation observed during the first trading sessions. The subsequent collapse of the Nasdaq is also well known.

The best comparison, however, is not to say that the current candidates are identical to the most fragile societies of 1999. This is not the case. These are much larger companies, with real customers, real revenue, and in some cases, significant operational strength. The most relevant parallel concerns investor behaviour. At the time, the excess of enthusiasm was mainly seen in the valuation of IPOs as well as in listed markets. Today, if there is excess, it seems more concentrated in late-cycle private valuations and in some of the listed companies already linked to the AI and infrastructure theme.

As Aswath Damodaran (professor of finance at NYU’s Stern School of Business, specializing in corporate valuation and corporate finance) reminds us, the subject is not only whether a company can one day justify a gigantic valuation. The real question is whether all the companies already valued as future champions can really achieve this at the same time. However, when an entire sector is valued as if each major player was going to dominate a huge market, expectations built into prices often become excessive.

What a Disciplined Investor Should Do

A mega-IPO should above all be understood as a valuation event, and not as an injunction to invest. It can reveal the degree of optimism already built into adjacent positions. It can trigger a sector rotation. It may force investors to revise their assumptions about indices and passive flows. But none of this requires an immediate transaction.
The most helpful step is to look at what you already have.

• Which positions have indirect exposure?
• Which stocks could be temporarily under pressure due to an institutional reallocation?
• Which parts of the portfolio depend, implicitly or explicitly, on public market acceptance of AI-era private valuations?

These are potentially better questions than whether to chase the IPO itself.

Conclusion

The next wave of mega-IPOs could be historic in its scale. But for most long-term investors, its main importance will not be the opportunity to buy a leading private company. It will lie in how these IPOs reshape prices, narratives and flows around assets that are already listed.

That’s why the right reaction isn’t usually enthusiasm. It’s clarity. Know what you hold, understand how the market might revalue it, and stay disciplined when the show starts.