The animated classics are NOT classified as musicals due to being mostly dialogue, while a stage production is mostly sung for 75-90% of its runtime. There is a difference.
Wicked would literally only rely on Defying Gravity or a mash-up of melodies from the movie(s). But it'd also require all new content filmed (or digitally created) for the Studio Tour (that goes for BTTF as well, unless it was voiceovers) which is why I don't see it happening as a replacement.