in 100% honesty, and IN MY OPINION I would not be surprised if we don't get one at all this year.
Between the budget cuts going on everywhere, the slowly dwindling entertainment staff (which they need a lot of, or a lot of the poor souls get stuck working 90% of the event) and the amount of complaints following last year's events (and the fact that there'd be even more this year if costumes for over 14 y/o's are NOT allowed) I can see wdw not doing it again this year.
Take for example the 2nd year of Villains unleashed! Despite it being a hard ticket event that was a large improvement on the year before, (and we had an ABSOLUTE BLAST) they haven't done one since.
I really do hope they do one again this year, costumes or not, I've gone to the last 2 and had a lot of fun at both! The Frozen theme certainly was lacking but there was only so much they could do for it. I think a more general theme, like "villains" or like "christmas in july" (aka..may...summer) would be one that you could end up having a lot of stuff to do. I think people also have been given the expectations of TONS OF SPECIAL STUFF going on when in fact, the special thing is that the park is open 24hours.