You mean 2.5". And those enclosures violate the spec in more than one way: first of all, pretty much all drives require a spin-up current of around 1000 mA, which is twice what current USB can provide. Secondly, the enclosures don't appear to even try to "ask for" that much power, especially not the (extremely non-standard) "Y-cable" solutions. I don't know anyone who's fried their USB ports with one of those things, but I certainly stay away from them.
To answer the original question: if they bring out a drive + bridge logic that consumes less than 900mA on spin-up (or a bridge board with a sufficiently big capacitor to cross the spin-up period) then yes.
