You know, it isn't totally obsurd.
I could see it happening, but I really don't think an entire Indy park could work, you'd eventually just start having empty space and re-hashes of old rides. Star Wars is so wide a universe there's probably more things you could do with that.
I don't think it's impossible, but it really isn't in Disney's best interest, I mean let's face it, the changes are drastic. They had to re-theme everything in AdventureLand