I suspect this will be revisited if all these companies are still 1T+ market cap 12 months from now. At some point the S&P will have to say the market itself has spoken and likely capitulate.
It really doesn't. The S&P 500 is an opinionated index. If you want total market, buy a total-market index.
My guess is S&P will stick to its guns, Anthropic will season in, and SpaceX and OpenAI (if it goes public) will stay outside for a few years.
The S&P 500® is widely regarded as the best single gauge of large-cap U.S. equities. The index includes 500 leading companies and covers approximately 80% of available market capitalization.