Any hotel, no matter where and what price, can get bed bugs in a room - unless they prohibit guests from ever staying there anyway. As has been said, the hotel doesn't breed them, occasionally guests unwittingly bring them in with them. It's how the hotel deals with the situation if it does occur that is important, and Disney are VERY hot on moving guests and eradicating any bugs as soon as they are found. I'm impressed that they went as far as contacting guests that had already left though, that's very conscientious considering they could have just waited to see if they heard from those guests first.
In short, there is no more or less a risk at any given WDW hotel, don't let it bother you.
Andre