This seems highly premature. Frankly, the only way he will stay and the only way the deal will not be done, is if he doesn't want to play for Man United that badly.
And why is that?
I think PL fans don't have much of a clue about Dortmund and just think they will sell if the price is right because that is what they do.
Which IMO is a fundamental misunderstanding....
They usually sell because they have to not because they want the money.
The only guy that was not close to running down his contract when he got sold was Dembele and that was because he basically went on strike and they got an absurd fee for him in addition to relieving them of the headache he created.
Almost every other player that they sold either went via release clause (aside from Haaland nobody has one anylonger due to that) or because they refused to extend their contract and only had 1 year left on their deal (Mkhi, Hummel, Auba,etc.)...
Aside from Dembele I don't think they have sold anyone by choice for the money.
So with Sancho who has 3 years left, why would they cave and sell him now when they can just keep him and get a similar if not higher fee a year from now?
And pretty sure Sancho wants to play in the Euros next season so him forcing a move at all cost is a dangerous game as well especially because Dortmund probably won't want to establish a pattern of players getting their move if they pull a Dembele on them...