I think Maxis have stepped up a lot this year with the sims4, we have gotten bunk beds, hair color updates and other good improvements. I have been positively surprised with some of their packs as well.
I do feel that the sims4 is reaching a bit of a "creative standstill" though because of their limited time and budget it does feel like some features are reused or not developed enough. And their lacking QA which are greenlighting things that should be sent back to their design and gameplay teams and them also missing bugs are also a huge problem.
A couple of years ago I wanted the sims4 to end, now I am a bit curious to see where it's going, that said if EA doesn't adress their budget and QA issues then that road is looking a bit dark where while we could get some interesting content every year, the game could end up in a pretty bad state. From what I have heard Maxis are opening up studios in Europe, have them work on the game as well, it feels like it needs it.
In my opinion, now is the time to add some last improvements because I don't think the game can handle many more years with the support it has. I am not in a hurry for the sims4 to end, but I also realize that the game will only get better with small updates and new features in every packs over time, and I'm not sure the game can handle that.
Cottage Living are showing a lot of red lights that we might reach too much content that the game can handle without some serious optimization. People have reported that the world is very laggy for them, the fridge is lagging for a lot of people, most likely because of all the recipes in the game now, people are experiencing more simulation lag and performance drops than ever.
So tldr, if support get's better for the sims4, then I'm fine with it staying for a few more years, if not. Then it's probably time to add some last updates that people want and then move on.