As far as I'm concerned there's already an overflow on the market besides shovelware, in the form of an endless pit of FPS, Racing and Sports games. Adventure Gaming has taken a serious hit and it's a damned shame.

As for a possible shovelware overflow, I think natural selection will take care of that since there's a whole bunch of successful established franchises out there that will continue to crank out sequels without motion control, people would rather buy that than shovelware.