Until someone else has a good world cup and becomes the next must have for Madrid.
If I was advising him, it wouldn't be to go to Madrid this soon. If he becomes as good as everyone expects, that opportunity will still be there. He can move elsewhere on a 5 year deal and if he saw it out and walked, he'd only be 23. But there's a chance that he won't immediately settle in Madrid with the pressure, at which point they drop him and he'd need to take the next chance he gets or he's out and down a level. Personally think the best for his development would be to stay another year at Monaco, enjoy the World Cup and then move, probably to a stepping stone like City or Chelsea, before the move to Madrid - Barca and Madrid still have that special pull that other teams don't, whether we like it or not.
Plus, if I was his agent, I'd want two big money deals to make sure I was getting a nice pension.