Yeah, it's a smart idea. Nintendo is only reacting to the market. The market loved classic 2d mario, so perhaps they will love classic 2d Donkey Kong and Kirby?
Donkey Kong Country is the safest bet. I can see it easily having 5-10m lifetime sales. Retro is a good studio and will make a quality game (they've proven that they can revive old franchises).
Before E3, I would have said that a new Kirby game wouldn't be marketable. But from what I've seen at E3, this game stands out. I think 1-2m is what I would expect from a game like this, but I wouldn't be surprised if it sold more than that.
Kid Icarus is a tough one. It really wasn't that popular on the NES (Hence there is no "Super Kid Icarus" or "Kid Icarus 64"). This will be looked at as a new IP for many customers. I imagine it could sell pretty well in Japan (it seems like a Japan-type game). Then there's the 3d aspect, which this game seems to use extremely well. Perhaps 1-3m is not out of the question.
