I was sure that I recently read (not from an authoritative source) that there will be a Marvel crossover, so you pick your superhero and then do missions to defeat the villains. Lots of scope for expansions. I didn't really pay that much attention to it so I couldn't even say where I read it.
Makes much more sense than D&D, which already has so much overlap in the lore that no one would notice it wasn't part of D&D if you didn't tell them.