They should just release a 15-20 E-shop game. The wipe out series did pretty well with this model. I think that this would minimize risk, and then they could accurately gauge interest. People clearly want it, and I think after Brawl and Nintendoland, people will know what it is/ be curious. A hiatus like this has built some interest, much like the Metroid Hiatus built anticipation for Prime.
They would make money on F-Zero.