If he goes to Juventus, for a permanent deal, then I am sure that they are going to actually get a great return, because of the first time ever he will be considered as the starting player for his position and not be doubted. He can play a lot better that way and he can show the world that he deserves to play, seems like a good deal for both.
Juventus is very smart in transfer market and they will certainly not sign a long contract with Sancho or officially buy him. The best possibility is a loan transfer and Juventus will assess Sancho performances within one season before deciding to purchase him or not. Even a loan transfer is challenging for them if Sancho won't accept lower salary than what he is receiving from Manchester United.
Juventus seems to be dragging their feet on this deal. I'm truly surprised by this, even though Sancho was willing to lower his salary to leave Manchester United.
In terms of individual quality, Sancho is indeed excellent, especially given his young age, which means he has the potential to develop further in the future. I agree that Juventus should acquire Sancho if they truly want to build a team for next season.
Sancho seems to lose his best skills and confidence so that he could not perform well in Manchester United and Chelsea after leaving Dortmund. Even a return to Dortmund could not help him reviving his career a lot and with his current situation and form, I don't believe that moving to Serie A that is a defensive league, will be a good choice for Sancho and it won't be a happy collaboration between Juventus and Sancho.