Mario Sports Mix, an arcade-style medley of sports games starring Mario and his friends, will be coming to the Wii in 2011.

A trailer shown at Nintendo's E3 press conference showed Mario, Donkey Kong and others playing hockey, volleyball, dodgeball and basketball in a lively, cartoonish style.
-Kotaku

This probably ultimately defeats the purpose of Martinet's voice acting for Paper Mario: TTYD2, however, everyone says it IS in prodcution, since a nintendo employee did announce it.