I'm definitely finding what others have said about it being a bit more simple and back to basics. In some ways it's really good, especially with the loading times. I do wish that you didn't get a loading screen in your own little "suburb" though - just those four neighbour houses.
One thing I like with the gardening is that, even though it does take a lot more time now, the grafting! I really dig that (pun semi-unintended), especially with it making new things. I would like a sprinkler back though, I think that would solve a lot of the time issues. But gardening has always been one of my favourite aspects of every version of the game. (I think my favourite thing to do with the produce was in Sims 2 with the juicer, you could only make particular juices if you had the ingredients. In Sims 3 it really only improved the quality of food, so having it reduce the cost in Sims 4 is kind of nice.)
Oh and on that note - there should be a bigger range of food qualities. I don't feel the same satisfaction watching my chefs gradually produce better meals when it's only okay, good and excellent. Gardening has more quality stages, why not cooking?
I'm also not a huge fan of the observatory or microscope. They're too huge, especially with the smaller lots, and so far I've actually never gotten any prints or anything from them because my sims don't stick with it long enough. So I'd like a small telescope back. The only really nice thing about the big one is woohooing in it, though woohoo in the rocketship is better (and how I'm fulfilling the nerd brain aspiration that requires "launch or upgrade a rocketship 5 times" for my astronaut's husband).
Things I expect we'll see in expansions: seasons, hopefully more supernatural life forms (I'd say aliens, vampires and plant sims for sure, though I hope they stick with drawing more influence from sims 2 over 3 for the plant sims), some kind of vacation thing like world adventures, pets, probably magic, maybe university (again, I preferred 2 over 3, I actually deactivated that EP fairly quickly in 3).
Randomly, one of the things I LOVE about build mode now? Choosing the height things on the wall sit at.