I don't expect Disney's attendance to fall but Universal attendance will certainly increase. We'll be going to Universal for one day during our Disney vaca in December just to see Harry Potter.
So, are you saying there will be more people coming to Orlando? Even if there is more venturing offsite (Universal), you think WDW will still be crowded? does that mean people will be staying longer??
Honestly, I don't know if anyone truly has the real info on that, besides maybe the booked rooms at the hotels...even that might not be a good indicator.