Prediction markets are not known for their subtlety. Right now, Polymarket traders are placing four-to-one odds that OpenAI’s IPO will close at a market capitalization of $1.5 trillion or more by the end of 2027. That is a remarkable swing from the 35% probability assigned earlier this year, and it tells you something important about how fast the AI investment story has moved.
As of September 2026, the contract tracking OpenAI’s closing market cap has crossed $233,000 in trading volume, a modest figure by Wall Street standards but meaningful for a prediction market focused on a single private company’s public debut.
What is actually driving the confidence
OpenAI’s March 2026 funding round was the clearest catalyst. The company raised capital at an $852 billion post-money valuation, instantly making it one of the most valuable private companies in history.
Then, on June 8, 2026, OpenAI filed a confidential S-1 with the SEC. That filing is the formal starting gun for a public offering process. Companies file confidentially to work through regulatory comments before going public, which means the document is not yet available to outside investors, but its existence signals that internal planning has moved well past the whiteboard-and-wishful-thinking phase.
The revenue story has followed. OpenAI is now running at roughly $25 billion in annualized revenue, fueled by ChatGPT subscriptions and enterprise API contracts.
Polymarket’s related contracts are pricing in a 95% probability that the IPO closes above $1 trillion, assuming it happens within the 2027 window. The $1.5 trillion contract is the more ambitious threshold, and even that is now pricing at 80%.
The math that gives pause
A $1.5 trillion valuation on $25 billion in revenue implies a price-to-sales multiple of 60 times. That is a number that would make even the most enthusiastic growth investor pause, because it assumes not just that OpenAI continues growing rapidly, but that it does so while also solving a profitability problem it has not yet cracked.
OpenAI is still posting GAAP losses. The company’s infrastructure costs, the data centers, the chip procurement, the electricity bills that come with training and serving frontier AI models, are enormous. Reaching profitability at scale requires either dramatically higher revenues or dramatically lower compute costs, and ideally both at the same time.
There is also a structural caveat worth understanding. OpenAI restructured its corporate governance in 2025, transitioning from its unusual capped-profit model toward a more conventional for-profit public benefit corporation. That shift was a necessary precondition for an IPO, since institutional investors need the kind of shareholder rights and governance clarity that public markets require. Without it, the S-1 filing would not have been possible.