Even then Man U could appeal for an extension of the transfer based on FIFA regulations article 4.6:
4.6.1 "A club can ask for an extension of the transfer deadline to register a player who has already agreed to terms with his new club provided there is enough evidence to sustain such claim."
4.6.2 "In provision of the clause above, a club can also ask a deadline extension if the failed transfer has a negative impact on the club's image and emotional distress on its fan base."
4.6.3 "FIFA must receive a written request to initiate procedures for extending the deadline. The selling club can appeal the decision with the corresponding documentation listed in annex G"
This could drag on beyond August.