He says he wants to return, yet he won't sign an extension. It's not like there's any negotiating over the dollars; the maximum allowed on both fronts. If he TRULY wanted to stay in Orlando, he'd just sign.
But, he wants to become a free agent, I'm assuming because he wants to see how badly Orlando's going to regress next year. And.... it's going to be a lot.
EDIT: In the end, I don't think Dwight wants to sound like a jerk to the Orlando fans. I'd be absolutely shocked if he wanted to re-commit to another five years; the team around him is a mess, and they don't have many options to improve it.
EDIT 2: The only reason I'd hold off on trading for Wade if I'm Orlando is potential changes in the CBA. Could well be that Dwight's looking at much lower "max" dollars under a new agreement. Given the likelihood of max contract values and guaranteed years being reduced, sure makes it more curious that Dwight doesn't want to sign an extension now, under the current CBA.