No, 2027 was never their median forecast; it was their modal forecast. See https://blog.aifutures.org/p/clarifying-how-our-ai-timelines...

It's more like it moved from 2028-2032 to 2030-2035 (depending on the author).

Fast takeoff was always only possible if you ignore all of physics and everything about how practical reality works, nothing exponential lasts for long in a finite system. If they believe that, then a certain level of self delusion is required anyway and you can ignore anything you like. Sort of like communists saying socialism will definitely work this time.

The book Superintelligence was so highly praised years ago but if you actually go and read the thing today practically all cases it presents read like raypunk retro-futurism that makes up imaginary fantastical nonsense in place of the missing knowledge it would've needed to make any sensible predictions. Practically none of its assumptions apply to LLMs as they currently exist, and some we've learned since about human inteligence are wrong too.