Now that's a shame! Maybe they'll introduce mini servos?
Well, you can sort-of do that now, with the SimDroid skin over on MTS2 (
http://www.modthesims2.com/showthread.php?t=42554&highlight=simdroid). It's a genetic android skin that you can use in CAS to create sims who would be normal sims in every other way. Like any custom skin, there's also a chance it could be passed on to kids.
Plus, it makes a real nice skin to use with existing servos, though they don't otherwise change their servo behaviors. There's a thread in Peasantry here about how to use SimPe to make this skin appear on a servo - you'd have to edit existing servos individually, so you can have some classic and some android servos running about.