1. Kurt tells some authority figure about the kiss, Karofsky gets expelled for sexual harassment. But I don't think that's going to happen because they're "exploring" the character more. Plus Max Adler has said that Karofsky will be in the superbowl episode. Isn't that in Feb.?
2. Karofsky isn't expelled but Kurt gets a restraining order. I don't know if that would allow them to attend the same school though.
3. Karofsky snaps and tries to kill himself (he may or may not succeed) and/or comes out and stops bullying Kurt.
Or, Karofsky decides to accept Blaine's help and becomes nice. Maybe even joins ND. But I highly doubt that would happen.