That's not about Bellingham or Haaland the last season that's about the Borussia Dortmund business they have, Dortmund is a team that grows young talents and then they sell these players to earn money. I think this if they change their plan any time soon.
They will not change their plans for the upcoming season. Dortmund will still be looking to make huge profits in each transfer window so it would be no surprise for them not to sell their star player. Their strength is often unstable in every season because even this season some of their important players have left and that is something that strengthens us if Dortmund will have difficulty winning the title next season.
But I am impressed with Dortmund talent scouts because they are very professional in bringing in talented players so they only need to polish their quality in 1 or 2 seasons until they become star players who are the target of big European clubs.