Possible? Yes, will it happen anytime soon? No. Theres hardly a decent, working DS emulator for the PC and the best one thus far on the market is closed source called No$GBA and that can play some DS games decently.
Also what about touch screen support? I can't see it being easy to use both the buttons on a wii mote and the motion sensor for the touch screen. Also it would be a bit overkill since the DS screen size is a bit small and resizing it to fit on an average TV would make the game look horrendous.
I don't see the problem with the touch screen and buttons issue.
There aren't very many DS games that make you use the touch screen, buttons, and d-pad all at the same time.
It's almost always the touch screen by it's self, the touch screen and buttons, or the d-pad and buttons with the occasional use of the touch screen.
All you'd need is the classic controller and a Wiimote for pointing.
Either way, I can't see a DS emulator on the Wii anytime soon, but it could be possible.