Yeah that's fine and all, however mobile phones and tablets are already (I think, but not a 100% sure) more powerful that either the DS or the 3DS, or should be very soon. Plus you can do other stuff on those as well, like make calls =P
Which is a long way of saying, it doesn't make much sense in today's (and specially tomorrow's) market.
But hey, we'll see... I don't see it working... I might be wrong. Time will tell.