The last rumor I heard (which is just a rumor) is that the earliest possible date was July 4th. If the rumors I heard about the massive amounts of damage to it are true, I'd think July 4th is far too optimistic.
But I know Disney will do everything they can to get the dragon up well before summer is over...if they go TOO much past your visit, then they won't be delivering her to the crowds "later this summer" at all! So I would hold out some hope, but realistically, there's no guarantee that they'll even have her fixed this season at all.