This rumor comes from a recent interview with Lucasarts, who would be the maker of such a game on the Wii:

The head of the LucasArts, the game division for “Star Wars” series creator George Lucas, told AFP a Wii game that lets players wield virtual light sabers is on the horizon.

It’s just a matter of time until we get a ‘lightsaber’ game for Wii.  Hopefully we’ll hear more at E3.