I personally don't see cars ever coming, how would that work with neighborhoods surrounded by water? Be stuck in just that neighborhood? Build bridges? What if the neighborhoods with no roads?
I don't see babies ever being freed either (although I hope I'm wrong). People have been asking for that since the beginning and 6 years later they have yet to do it.
They have stated before spiral staircases are "too hard". One Guru in an interview just recently stated something to the effect of "Look around at the modding community, if they haven't done it yet that means it's hard to do"
The NPCs I could see them adding, now whether those would be base game free updates or come in some pack that's the question.
I could see them doing a Winter Vacation world, or a Casino lot with one functional game play item, I don't see them ever making a casino with 3-4 "casino games" with animations tho.
And, I for sure don't see them ever adding any type of color wheel (unless it was forjust the skin tones) and not for other CAS/B&B items, they would have to redo every texture for that, there has to be channels for that in the texture. TS3 textures had sections of it separated and put on a channel that could be recolored/retextured. TS4 textures are one single texture. I just don't see that happening, not this late in the game.
But, hopefully we'll get some of that stuff when TS5 releases.
