Open world is possible, depends on how they would design it, games have come a long way since sims3 which was released in 2009.
I'm tired of loading screens, I think the solution in the sims4 works when playing a single sim or when traveling with a few sims but if you want to play an entire household and have them do things while you are visiting another lot like a night club, the whole system falls apart. Sims will stay awake at night and will not have enough needs taken care of if you wanted to do something with them the next day.
The next sims game needs a better system in my opinion, we need a better system for people who want to play larger households and also allow us to visit community lots and other lots without having to reload the entire neighborhood.
It will be a very limited life simulator game otherwise.