I question the wisdom of this from a crowd control standpoint. As a cast member I worked operations/attractions and also in close proximity to some of the Magic Kingdom mountains. It's generally believed that a HUGE portion of a park's attendance are, at any given time, contained within the queue lines of the various attractions in a park. For an attraction that puts through 2,000 people an hour, with a wait of an hour long, that means theoretically there are 2,000 people standing inside the queue of that attraction (I say "theoretically" because FastPass messed those numbers around some).
On the rare occasion I witnessed, say, Thunder and Splash Mountain being evac'd and having their queues emptied at the same time (it sucks but it happens), you could tell the park almost couldn't handle the sudden addition of the several thousand guests being emptied into the walkways. If every major attraction were to switch to this "queue-less" system, and effectively turning the walkways of the park itself into the queue for the rides, I can't even imagine how much more crowded and insane the parks would feel. On busy days, there could potentially be thousands (or even tens of thousands) more people roaming around the outdoor areas of the park that would otherwise be in line for something. Factor that into how crowded the parks feel already, and I could see this causing quite the crowd control problem.