Okay, here's a little prediction from me.
I think the engagement / wedding will be called off, and Carrie will split up with Joel. I don't know when - could be days, weeks, months.... but it'll happen.
And then, Joel singing You'll Be Back night after night will be poetic irony in its truest form. It will be equal parts pathetic, worrying, sad, and hilarious. And he'll probably start acting out the song in a much more darker / bitter way as he tries (and fails) to deal with the heartbreak.
You heard it here first! Grab your popcorn, folks!