I think they are wisely waiting until they finish all films, so the extended double dips don't effect future releases. (If they released extended HP1, 2, & 3 now, who would buy the theatrical DVD of Goblet of Fire? Anyone with have a brain would wait after being burned 3 times.) It's smart of them (uncharacteristicly so), but it blows for us.
If you've seen the ABC Specials of the HPs, you can see some transitional elements between the deleted scenes not on the DVD's (or ADM's edits for that matter). Nothing serious, just stuff that smooth out the cuts. Someout door beauty shots and such. It basically suggests that they are all ready to go with extended cuts.
Most importantly, I would NOT expect a DVD release. It might be an added value they try to push into WB's first HD-DVD releases...
Which brings me to: