I play tons of other games (sneaking in Deus Ex: Mankind Divided and getting my butt handed to me in Darkest Dungeon right now) and only occasionally jump back into the Sims. But when only talking about the Sims series...
I don't own TS4 and am not planning to get it either. While I do like the looks of the sims and the new Create-a-Sim options like how you can edit their bodyshape, walk style etc. (though the lack of create-a-style is a minus), there's nothing in its' gameplay that entices me. Well, maybe the vampires & parenthood packs because I like how they enhanced something I like in a more focused way but otherwise... meh. So I'll stick with TS3. I was very late to start this game anyways so I still have lot to do.
Maybe if they released TS5 which would enhance and combine all the things I like in the series and feel like a true successor to TS3. CAS akin to TS4, Open world, customizable Storyprogression, Create-a-style, waaaaaay better optimization than in TS3 and generally more complex interactions/gameplay. I personally love the sims and their interactions the most over things like build mode stuff so for me it's especially important that I can create interesting characters and relationships. I'd also like some more challenge, hardships and unpredictability but I guess that's not for everyone and mods can always help me with that.
I am skeptical about the direction of the series, however, and would not be surprised at all if the same or even worse systems were in place in TS5 than there is now i.e tons of content left out and then divided between little stuff packs instead of it all being in an expansion. I guess one could argue it let's you specialize your game and I'm not complaining with stuff like TS4 Vampires. I'm talking about the stuff like they did with pets. Only get cats and dogs in the fully prized expansion, then have to buy a stuff pack if you want "rest of the pets and items" while in previous games all of them and more were in one expansion. If these kind of practices were to be the norm... yeah, certainly would lower my enthusiasm.
