I dunno, if you think about it,they've had pop songs for themes before, just that it was by a j-pop star.
I don't really know how I feel about the song being the main theme since they always try to make instrumentals and other songs that coincide or build up to it, and I just don't think an instrumental of this song would be compelling enough for the game.
But I agree, we should wait and see what the games like before judging.