There is a lot of stuff we don't know yet and a lot things that we do know which actually including a major difference to game play and all that
Confirmed things-family visits, able to create your own holiday in addition to pre-made holidays (if we can create our own, we probably can take out holidays we don't want or change them. We get more customization, which is the one thing many people asked for along with weather). Sims can also be able to skate, build snowmen and snow angles, pets react differently to weather (some enjoying it more then others), new career, etc....probably tons of other things that I missed. There are also the return of sprinklers, swings, etc...we will be getting a kid pool for toddlers, etc...plus the return of beekeeping.
Some things might actually come with the next patch. One confirmed thing is glass roofs; but we don't know what else (from what I heard about with Sims 3, they got online dating, so that possible to make a comeback. We have to wait and see). We saw 1. trailer and a lot can happen by the time the game does come out and as more information is given to us.
