Cool. I hope they take out the bloat on the expansions (needing seperate executables and support files for everything.)
And if it was 64 bit only that'd be nice, though probably not bloody likely.
And if they could engineer it so adding custom content didn't massively slow the game down, that would be worth a new version.
For anything else, I don't know if the designers would be on the same track as me. The Sims, since the first version, has become much more of a dollhouse-oriented title, marketed to teenage girls, than an interesting simulation game. Werewolves, vampires, fairies. Katy Perry theme DLCs. I would want, for instance, doing laundry to be a necessary part of the game, and the player to have to go our and buy clothes, and home construction to take time and make noise. I expect the designers would reject that as boring, but if Will Wright hadn't been involved in the first game, you probably wouldn't need to use the toilet either and old newspapers wouldn't collect on your front lawn.