I'm personally hoping for a Holidays 2014 opening.
I know there's an "LOL" at the end of that statement, but it's possible. Though, I hope the opening won't be that staggered... I'd love it if they could finish the London facades and the whole waterfront area first, and have that unveiled ASAP, then finish Diagon Alley, and grand open that whole area and the HE all together, not in more phases.