With SpaceX, now Anthropic, and soon OpenAI, we're seeing 3 of the largest IPOs ever. Will existing institutional investors trim other positions to allocate a lot of capital for these mega listings or is this not a concern?
There is an open question about the ability for the market to absorb these three. Absolutely an open question.
There isn't really a question. The market is huge and can absorb it, the questions are around the specifics - can pension funds invest if the company has a junk rating (no), is the valuation justified based on current finances etc.
The demand for the particular company may not be there, but that is different from "the market". There's plenty of capital to go around.
I would expect "largest IPOs ever" to continue to occur often in the future, just as we have through out the history of the stock marker.
I wouldn't worry too much about OpenAI; they seen to gave deferred their IPO until 'sometime in 2027'. At this point they're basically at the mercy of Anthropic, since if the Anthropic IPO goes poorly or gets pulled then it's going to look to investors (and everyone else, frankly) like OAI will be dead on arrival, too.
Fun times ahead, for sure.