Sadly to accept but soccer this days is all about money, and if, IF Messi goes from Barcelona he will go to a team that offers more money for him...
I mean, as soon as the news say that Messi is free to joing any club, Inter, Mlan, Chelsea, Man U, Real Madrid and every team in the world will want to buy him... and sadly, Juventus don't have (or don't want) that kind of money to compete with big spend teams...
And besides, I still don't think he will leave Barcelona, at the end they will find a solution to keep him.