Hmmm...
With Storm's vehement reaction and revulsion to the very idea of a cure, it would be interesting to see how she would react to Rogue's decision to take it. In the movie, Storm felt very passionately AGAINST the cure - and I suppose it was no accident that it was Rogue who was by her side at the doorway as she was ranting about "There's nothing to cure. You know why? Because there's nothing wrong with you!"
Technically - and I know this may sound heartless - as someone else pointed out, the Xavier Academy IS a School for MUTANTS. Having taken the cure - and assuming the cure is permanent (ok, lots of debate over this point, which I won't go into here) - then Rogue technically no longer belongs to the school, and yes, has to go, sorry, shugah.
Interesting plot twist, though, would be to have a de-mutanized Mystique in the human form of Raven Darkholme somehow crossing paths with the now-newly-homeless Rogue (oh, sorry, MARIE!). In the comics (yes, we always have to refer back to the source material, don't we) Raven worked as a government operative for years, and it was interesting how, in the movie, she was the one who provided the government with the location of Magneto's new camp. Mystique's talents aren't limited to shape-shifting; she's a cunning intelligence agent and a formidable fighter, and working as a Special Ops agent for the government - pro-mutant or con - doesn't seem like a stretch. She's also spoiling for payback against Magneto for his brusque rejection of her, so it wold be interesting to see her working alongside Trask in the creation of the Sentinels.
Anyway, Rogue (oops, sorry. MARIE!) wouldn't know the human form of Mystique from a baked potato, and could easily be taken under Raven's wing and ever-so-subtly brainwashed to turn against her former colleagues in the Xavier Academy. Raven could use soooooo many motivations in this, i.e. "They kicked you out because you wanted to be normal", "Bobby just wanted you for sex.", "That nasty nasty Kitty girl stole your boyfriend, AND she still has powers. What have YOU got?"
Hmmmmm...