Things I will miss in TS3:
-CASt (sometimes. I don't think it will bother me that much once I start playing).
-Pools (But I think we'll get that later).
-CAW (But who's to say that TS4 won't have BETTER worlds, therefore I won't feel the need to have to create my own. Because lets face it, TS3 worlds were pretty bad once you had EPs. You couldn't have everything in one place).
Uhhhh, yeah that's it. I'm personally not bothered by the lack of toddlers, and babies that can go places, because I never play toddlers in my games! No family tree is no problem either, honestly.
Don't hate, I'm just giving my personal opinion :)