Yes, if Disney runs the site in a way that promotes open debate and is also open to criticism of its policies, procedures, direction, etc, then yes, that could be a very valuable tool for providing feedback.
Again, though, I'm not at all convinced they would run it that way.
Further, I'm a little surprised they are considering jumping into the game this late. The established sites already have plenty of pro-disney talk, and they have huge followings. It won't be easy to get people to switch.
Of course Disney could play hardball and start enforcing all of its copyrights, but that would make them look like a bully and would anger many people who have been their biggest supporters and fans.
I think Disney has the ability and resources to do a great job with something like this, but if they want to supplant the fan sites, they would have to really change the way they view things like rumors, information sharing, open discussion, etc.
Same with their podcasting. They have official podcasts, but its the fan podcasts that are the most popular.
If they ever actually move forward with this, I guess we'll find out.