A new patent has recently been filed by Nintendo, which reveals a new motorcycle game. The patent illustration shows a person using the Wii Balance Board to control a motorcycle, as well as using the Wii Remote and Nunchuk attachment to presumably control the accelerator and brake functions. Another illustration also shows a single Wii Remote being used to play the game.
The idea for the game comes from Nintendo Software Technology, the same development team responsible for the Mario vs Donkey Kong series and the unreleased Project H.A.M.M.E.R.
Nintendo also had ideas that incorporated other Balance Board features in to the gameplay. For example you could jump from ramps and then you would have had to balance the weight of the bike to get a good landing.

No official announcements about the game have come from Nintendo and it's unknown whether this will be released.