I'd be surprised if he did do at this stage to be honest. He genuinely seems to love the club(constantly winning trophies and earning millions also helps that of course!) and the only time I can really see him leaving is at the absolute end of his career. If that is the case though, then hopefully he ends his career in Argentina rather than somewhere such as China or the USA.
It would be great if he actually retired at Barcelona as a one club man though and it's unfortunate that Iniesta and Xavi didn't do the same, rather than leaving to Qatar and Japan. Same with Gerrard when he left Liverpool in order to move out to the states. In many ways I regard them as being one club men still, as they left to semi-professional leagues in order to relax and end their careers with a nice pay cheque, although in the classic sense of the word, they won't be regarded as such unfortunately.