The club can't sell a player against his will which was well seen in the case of Bale.
This will certainly not happen here because both fans and journalists are putting a lot of pressure on the management to extend the contract with Modric.
Once you fulfill your dream and play at the Royal Club, any other club can't offer you the same.
Player like Modric will accept to leave the club if he does not feel respect from club's board. Or if Modric still has ambition to fight for a position in main squad and want to enjoy happiness while playing on the field in real matches.
I don't think Real Madrid or any of the team would have a principle or strategy of insulting or treating it's players in a bad way. Real Madrid had been reigning the top position in the league and a consistence penetration into the UEFA league for many years now. And with current team, they have achieved more with whatever they have and Luka Modric has been the heart of it. The association is mutually beneficial as he's now been considered a leading figure in a top team.