Not the motion controllers themselves (or lack of, in NATAL), but the fact that if both of these companies release this huge addition to their console, they risk following the same footsteps of other console makers who tried to update their consoles with an add on?
I mean think of it, if there are games that can only be played via Sony's magic wand or NATAL, that means that the sales for it aren't just limited to the user base of the console, but the add on itself. And how many games can be released for the motion controls? The big problem is a major division of not only who has and who don't have the motion control add on, but the division of the library. And the division will only mean that while Nintendo has a motion control console with an entire library dedicated to its motion controls, there is the risk of less than half of the releasing games featuring motion control.
And I can't really see games that make motion control an option succeeding that well. You can't just tack on motion control. We saw how that fails misserably with the Six Axis. Controls are an essential part of a game, and trying to work 2, radically different control schemes seems to be incredibly difficult and unrealistic.
I believe that people shouldn't be looking at NATAL or Sony's magic wand as a potential booster for this gen's cycle, but should be used for the next gen console.











