He is able to works together well so it is only natural that Real Madrid extends his contract because Real Madrid wants to achieve brilliant achievement with Ancloti.
Or this might create a new rumor if Brazil will make an offer to Xabi to manage Brazil's national team? 
I think this is not in line with what Dortmund achieved in the previous season because we know that Dortmund's environment, which always sells its talented players to gain financial gain, cannot make its team continue to maintain the same performance. I don't think it's a new secret and everyone knows, so yes Dortmund will still be a strong team but not with the consistency they have been better from season to season.
The other teams are same, they're making money by selling their top players. Dortmund could keep the players, but this will make the players will not happy if they want to join other teams that convincing. So I guess that's how it works, if Dortmund can't get a title, they still can make money from it.