Now, obviously I don't work for Disney, so I could be wrong. The fact that they're starting to promote the first three seasons again could show us that they're going to release the last two in the foreseeable future. I don't actually know how far they got in terms of clearing the rights to songs and all that. But, at this point, unless they only plan to release a limited number of copies, I doubt this would even be very profitable anymore.
It's been years since season 1-3 came and DVDs are dying out, so it seems unlikely that this'll happen. If they are released, it'll most likely be on a streaming service. And in fact, i'd argue the fact that the episodes are still online and Disney hasn't taken them down for copyright shows that they probably don't have much hope to release them anytime soon.