Superpowers? Slight gameplay change (which, from the video reviews I've seen thus far, affects the gameplay in a big way).
The story? Very different from any Saints Row game in the series , it may not be unique in the Gamesphere (Another Dee copyright

), but it is unique within the Saints Row franchise.
The level design? It seems to have been designed with the super powers addition in mind, along with the aliens (scaling), which implies change (not necessarily big changes).
I don't know man, this seems like a game that is different from Saints Row The Third, yet it still retains most of what makes it a Saints Row game.
Changes in how you play the game, and changes in the story and its scope. Any more changes could probably result in a new game, that wouldn't be a Saints Row game.
... Not trying to convince you to look forward to it, just questioning your assertion that it's the same game as its predecessor.