According to a “French Source” a new Mario & Sonic at the Olympic Games title is currently being developed. The new game will most likely be based on the next Olympic Summer Games being held in London in 2012 and is scheduled to release in 2011. Further information on the rumored title is currently unknown including the platforms that this new game will be available for.
Past Mario & Sonic games have been made available for both Wii and DS. It is likely that this new game will be for Wii but who knows if the portable version, if there is one, will be for DS or 3DS. Time to start speculating!