The problem is also of costs, but this won't be a problem forever: if nobody does the mistake of starting next gen too early, each competitor will be able to offer a complete controller set, adding what their respective sets currently lack without making the costs and the entry level price skyrocket. In the meantime, each one will have games that really shine only in a subset of all the possible motion controlled games. This won't be pointless, by starting now, MS is taking on its shoulders the effort to make depth detecting camera solutions' costs drop, while Sony is giving a little but welcome help to the adoption of precision wands, that are a little bit left behind because on Wii WM Plus arrived later and 3rd parties preferred to use just WiiMote whenever it was "good enough", to enjoy a wider user base. Finally, both Nintendo and Sony are now contributing to increase production and use and decrease costs of gyroscopes. When next gen starts, adding a wand to a camera-only solution, or a camera with depth detection to a wand-only one, or adding depth detection to a wand plus simple camera one will be a lot cheaper than now. BTW, Sony has the opportunity of completing its own control set with the smallest cost, doing it it could receive 3rd party ports from whichever else platform, while should MS and Nintendo stick with their own solutions without completing them, they could receive ports only from the subsets of 3rd party games running on Sony consoles and using only respectively the camera or the wand.
Edit @damndl0ser: I just read your post just before mine, I agree (I wrote something similar to what I wrote in this one also before, in this thread or maybe in another). BTW, most users aren't interested in console wars, they'll just prefer that their console have a complete control set, using the right feature for each task. And as I wrote, still right now offering a complete set would be too expensive, next gen it won't be anymore, and in the meantime each competitor can start getting part of the job done. And having a longer experience on different parts of what will be the motion control of the future, will help at least to keep some welcome differences in each competitor's 1st party games library.
