The Ones That Will Probably Happen
Before diving into what won't happen, let's just quickly run through some of the unmade films that do have a chance of making it through to the real world.
Pocahontas is probably the most high-profile film to not have any continuation announced, and I'd be shocked if Disney aren't working on a way to make the sensitive story work.
Lilo & Stitch may be a strange film from the 2000 dark age, but it's on the better side of that era and has such an interesting central concept (E.T. in Hawaii) that it would be a waste to not revisit.
Tangled and Frozen are no doubt pegged for the treatment, with the studio just waiting for enough time to pass for them to go from hyped releases to genuine classics. As for the other recent hits - Wreck-It Ralph, Big Hero 6, Zootopia - they seem constructed to exist as animated films, but despite being less likely, it's too close to release to really strike them out.
There's also quite a few that have potential and can't be fully ruled out:
Despite their being two Hercules films in 2014 (neither of which were great), the Disney version has such strong characters and style that properly done it could be a solid hit. The only barrier is making the strange Vegas quirks work in live-action.
The Princess And The Frog may already be a major reimagining of a classic tale, but The Frog Prince is just too weighty a story with Disney potential to rule out.
A sci-fi Treasure Island is a concept that is both interesting and, more importantly, very Disney, so while that movie is pretty forgotten, it'd be ripe for the redo. The same goes for Atlantis, which didn't work as a film, but has a strong name and looked great (a major factor here).
And, finally, I guess there's a way to make The Hunchback Of Notre Dame work. It's not as obvious, but I can't rule it out.