I think Sergio is happy being Sergio, he's one to those players whose found a home, is getting paid incredibly well and just content. Apparently he's such a nice guy (outside of the pitch anyway) he's not overly ambitious. Barca wanted him ahead of Suarez and the guy didn't even complain when City told them he's not for sale. Bearing in mind himself and Messi are best friends, it would have been easy for him to kick up a fuss and get the move.
We got really, really lucky with him, Silva and Megamind, 3 of our greatest every players and never a whinge about moving on from any of them. All have been very loyal to City, I suppose the wages we offer help.