The chance of that happening are close to zero. There is no realistic scenario for me how the club could become the driving force for a transfer in the next years.
Some people underestimate what kind of standing Hummels has for Dortmund. Not only among us supporters, who basically view him as the player version of Klopp in many ways and respect him more than any other player. His standing inside the club and the team is immense aswell. He was the undisputed leader of the defense at 20, part of the players council since 21, the actual leader of the team on the pitch and primary spokeperson off it for at least three years and is now also officially captain.
He is our most important player, period.
At least part of the reason why Hummels is so loyal is because he knows that and clearly enjoys this standing. He is Mr. Borussia for a lot of people and he always stated that his role in titles is way more important to him than the sheer number of them. He does not want to be one of many top players, but a clear standout player and face of the team. His desire for responsibility and recognition makes that pretty clear.
Money will never be the main motivation for him. He has proven that by turning down more lucrative offers several times. He is also not influenced by an agent and knows fully well that he is not forced to earn as much money as possible because his intelligence will allow him to make his way beyond his active career. Not to mention that Hummels will probably always be part of the top group in terms of salary in Dortmund. His next contract, the biggest of his career would include a hefty pay rise if he decides to stay given that we clearly plan to vastly increase the wage bill in the next years. At that point Hummels will earn money in a region, where two or three more millions won´t make that much of a difference anymore.