On the other hand, this now means outside of the World Cup, Messi's won everything in football. At this juncture he's as likely to just want to stay put & see out his career at Barca, as much as he might just want a final challenge before the curtains come down on his glittering career.
I'd be ecstatic if he decided to move on & came to us, but not surprised in the slightest if he decided to stay put. It is what it is. Messi will do what suits him best at this stage in his career. Messi isn't our future. If he came he'd be the cherry on top, not the player we build our team around for the future. In this respect we have other more pressing issues like a world class striker & a proper specialist world class left back.