Well the game is out and luckily the rumors weren't true.
With a medium-density city, I get about 40 FPS @ 4K in the sequel. With the same-sized city, I used to get 20 FPS in the original, so twice the FPS is a massive improvement IMO. But people are still salty cause we live in a world where anything less than 60 FPS @ 1440p is unacceptable. Which is stupid as fuck cause you don't need 240+ FPS in a city-building game with next to no action in it that would require such a high framerate.
It's already kinda annoying not to have all the old content but I can see the reasons behind that. But a new game starting from scratch of a genre they are experienced with should have much better performance now that there aren't all those additional mechanics. Failing at both of these is just an utter disregard to their customers.