Liam's gonna realize fame sucks and he's gonna erode himself away from the spotlight. Zayn's gonna do the same, but he's gonna live in Paris like a true artist, but with a moderately successful R&B album. Harry will try to make it, he'll do alright, almost like a Kelly Rowland success. Niall will be Ed Sheeran's BFF, and that's what he'll be known for. Louis will be like Joey Fatone. He will host game shows and do small acting gigs to stick around.
Pretty much what Ferst said, but a little more fun.