They probably started pushing Kitty because Bendis happened to be a fan (he's also the one supposed to be doing her movie, though I wouldn't expect it to happen now that the Disney/Fox deal has become almost a formality). So he used her in All-New X-Men (causing Jason Aaron to have to swap in Storm for her in Wolverine and the X-Men) and then Guardians of the Galaxy. When she came back to the X books, they had Storm and Kitty switch places again. Whether that was Guggenheim's choice or editorial's I don't know.