I do not think Superheroes would work in a game like The Sims and I really hope they won't "waste" an EP on it :(
Don't get me wrong, I do enjoy a good superhero-movie once in a while, and who doesn't like the idea of having superpowers and fighting evil! However, imagine the extent they would have to go through to make it continuously interesting - I don't think a superhero just goes to work 9 to 5, mon-fri completes some tasks and then go home. I think they would have to do something similar to TS3 Ambitions where jobs would "pop up", however that would be a bit limiting in TS4 worlds and was a magnet for bugs and glitches in TS3 and would most likely be so in TS4 as well - because it's not a game built for it IMO. I guess it could be kinda cool as one of those Stories-packs they did in TS2, but I seriously doubt they would do that.