It's not to be looking for a club that he will be among the first eleven, Sancho needs to fight for it by improving his performance and take his career to the next level. Otherwise, if Juventus sees that he is not playing as expected, they'll put him on the bench and replace him with someone else. Sancho have been moving from one club to another without any improvement to become one of the first choice for these clubs.
Sancho must strive for this to remain a regular in the starting lineup of the team that signed him, and I don't think it would be bad enough if Manchester United actually sold him to Juventus. The only requirement for Sancho to remain seen as a great player and not be discarded from the starting eleven is to play his best in every important match, as this will certainly attract the attention of the coach and team, who will not let him go to another team in the future.