I like the points you make, specially about it coming out in the "wrong" moment in time. It would suffer from microtransactions like TS4 suffered from the online fever (which ended up not happening but wasted their time and resources).
I think the art style of TS4 is really good for a long-term game, it doesn't look dated since it's not "realistic". This game will be active for longer than any of the previous ones. The game is in good health and I would guess we'll have at least two more years before we start hearing stronger rumours and leaks about TS5.
I still think it will happen but I don't know what direction they'll take this time.
I really hope they don't go back to "realistic" looks (TS3 sims were so ugly! and I hated their hair!) and they keep it single player, of course I also don't want any microtransactions.