In his recent interview, he basically said he likes life here more than Spain, because he can live a quiet life without hassles. The only ? would be his son Benjamin, but AFAIK he isn't in Spain but Argentina, and is over to see Sergio regularly. I think he'll be here for a while yet. Even if Real Madrid offered a world record fee... why? What do we gain by selling him? Can you imagine trying to replace him? I guess Luis Suarez would do a good job in a similar role, but Aguero is the club's modern day icon and you don't casually sell such a player.