Why is Henderson going to agree to that? If Henderson wants to keep progressing and have a chance of being England's #1 next year he's not going to be happy to sit on the bench for the year.
It's like when Chelsea got Courtois back from Atletico, they brought him back to replace Cech, and we need to do the same with Henderson, he's been far better than De Gea this season, it makes no sense to think he needs bleeding in, that's why he's on loan in the first place.
Knowing Utd though we will take the easy option and loan Henderson out for another season to be made to look like mugs for another season.