I'm hoping this is a joke. If it is, I guess joke's on me.
If it isn't, I'm sorry but you need to go get some ice because you're gonna get BURRRRRRRRNED!!!! haha j/k
That will NEVER happen. I apologise for being so blunt, but it won't
To emulate another system, the host system (Nintendo DS in this case) needs to be about 5-10 times more powerful than the system you're tying to emulate (Wii or Xbox 360 in this case)
That being said, nothing is IMPOSSIBLE, but we probably won't see that kind of backwards compatibility in our lifetime.
Nice thought, though!
Besides, the cost of a Wii or an XBOX 360 are so cheap, why would you want to emulate those systems and lose some compatibility?