Personally, I would love to see a Star Wars game using the THS system. Unfortunately, this will never happen for obvious reasons. I like FFG's games a lot, but the Conan/THS system is just so elegant and stream lined, it would be perfect. The system is really great for any kind of pulp fiction, though. Indiana Jones or Hellboy would also be cool, especially since it seems like FFG isn't planning on bringing Tannhauser back. Although, maybe Indy wouldn't really work, since he's such a loner. Classic X-Men would be great, too.
Also, just in case you hadn't heard, but there actually is a John Carter board game coming out at some point from Modiphius. I have no idea when, though.