I think the big 3 are cartelizing and starting to ratchet up costs. GPT5.5 is not easily distinguishable from 5.1. I would it be shocked if we hit the ceiling and everyone is quietly positioning for the exit.
I don't understand why everyone thinks there is a ceiling below human-level intelligence, when we have an existence proof that human-level intelligence is possible.
This is very napkin math, but the human brain has about 100 trillion parameters. Even the biggest models today top out at 10 trillion parameters. I think it's reasonable to assume that models need to be at least an order of magnitude bigger to capture the complexity of human intelligence, and probably a lot more.