I remember reading something a while back about their contract obligating them to put out one album a year for a few years and if they split up before then they stand to lose A LOT of money. Dunno if that's true, but it would be a good effort to keep the band together while they explore solo careers for some of the members.
Neither of them should go solo, they should just squeeze as much money as it is possible from their band career because teenage fascination never last (Justin Bieber). Once one of them goes solo, the band will flop and the solo one will flop as well.