If I know anything about Apple, Apple will add USB 3 *if* it wants to *when* it wants to.
In short, it's not a given. Apple doesn't use Intel motherboards in their machines (at least not any models I've pried open) -- they use custom motherboards. So they're under no obligation to use any particular feature of a chipset if they don't want to.
But I'm not saying they don't want to, maybe they WILL add USB 3 to machines this year. But I really wouldn't take that for granted -- although USB 3 is backward-compatible in terms of speed, it doesn't use the same plug, meaning new cables for everyone, and it's pretty large as a connector -- not exactly the direction Apple tends to go in.
So far I've heard absolutely nothing from either the supplier's grapevines or the rumour mill about USB 3 on Apple machines, which is unusual. Maybe it's a fait accompli, or maybe they are going to stick with TB and USB 2 for a while yet. It will be interesting to see which way they go.