I never played TSO...but i played secondlife (which apparently alot of TSO players went to that when it died) Personally I dont trust the simming community to have that kind of online game i dont think it would go over well with ratings and all.
as for the sims 4 ingame game (well that sounded odd) i thought it was the sims 1 which since the sims 1 was a hit and the sims online had alot of backlash i can see it being the sims 1. besides i think i saw magic town at one point.