Winx Club season four is, as we all know, taking a break. The last episode provided a sort of "happy ending" scenerio for the veiwers, so I can only guess that events will intensify when it picks back up again. Today I'm going to offer a speeculation:
Mitzi and Brandon. They were a really short-lived, unlikely couple. This subplot was unusually unimportant. Seeing as Mitzi appeared as an antagonist in the opening credits, we can only guess that even though her relationship with Brandon is dead, she's not gone for good.