I think the next is Act II but the return will come after with unreleased from the fame monster era! The Fame Monster need a sequel! But the return cover it's fake she have BTW make make up and antigas mask!
I love the idea of THE RETURN OF THE MONSTER. The artwork shown is amazing and I believe it would be a great idea to release an album/EP with such a title whether after ARTPOP or lets say 5-10 years from now.
Act II for sure. She's been talking about it and I'm sure there'll be more volumes of ARTPOP. As for The Return of the Monster, I think that may either never happen, or soon, or maybe a surprise. Who knows..