TS4 has a lot of limitations engine-wise (closed world), town design (very few 64x64 lots), and several shortcomings (emotions overriding everything, traits being irrelevant, and more).
But it runs way better than TS3 (probably due to the closed world, though), and the 'world-hopping' is a feature I'd love to keep in TS5 (many smaller towns with each its own setting and weather you can freely move between instead of a single large world).
But without TS4's CAS and build mode (drag-and-drop room moving and resizing, the eventual stairs 2.0 patch), I won't even think about playing a potential TS5 game. And I wouldn't play it until weather is implemented (which tends to be further 2-3 years down the line)
Realistically, there are some things TS4 is missing and that could still be added in future packs, but it's also obvious the game is becoming dated. Yet, I don't think a potential TS5 game would be ready enough for me (given the usual base game content and the packs I consider a must-have) sooner than in 5+ years - by which time, who knows if I'll be interested in playing such a game.
