If you think about it, it may actually benefit Nintendo if Sony and MS rip off their controller idea. The reason is multiplatform games. Right now when a game goes Multi-platform that means it comes out on the PS3, 360, and PC but not the Wii. One of the main arguments for why this is the case is Nintendo's weird controller and 3rd parties obsessed with either making use of that or bypassing the Wii entirely.
But what if motion controllers become an industry standard? Then 3rd parties are forced to deal with it whether they want to or not And maybe, just maybe, this might result in more games trickling onto the Wii.