I doubt we'll see a decent 360 emulator for at least a decade. I doubt we'll ever see a PS3 emulator, period. Architecture is simply too damn hard to do in software. Emulating all the PPE's of the PS3 and keeping the entire state coherent is going to take more processing power then we'll have avaliable for at least the next few decades.
I mean, sheesh, we have enough trouble emulating the PS2's 300MHz main CPU. You think we're emulating the PS3's 3.2 GHz SPE/8 PPE architecture anytime soon?