He has proven himself to be a good player at Dortmund, and if United doesn't want him then that's their own problem. However, United is not going to let him go for cheap, they are going to ask for a good amount of money without a doubt. Not saying that it would be impossible for Dortmund to pay up, they may end up buying him anyway because they made so much money from previous transfers so they should have some money.

But at the same time, I feel like we are going to end up with something much bigger and better if they get Sancho back, because they can sell him again in the future if he keeps playing well. All in all, it would be a good decision for Dortmund, they would get someone they can actually use very well in the end.