He deffo should not come back, if he is guaranteed first choice he should stay with them, it will give him incredibly valuable PL experience, him and Karius are the same age (23) and we can't have two young keepers on the bench doing nothing, it is a waste of valuable time to gain experience.
If things keeper wise stay the same get Migs as starter unless Karius overtakes him for whatever reason, Karius as cup GK for all domestic cups etc and Ward at HTAFC as first choice, that should ensure adequate experience/playing time for all