That doesn't really make sense. If he doesn't sign a new contract with Saints then any club can sign him for free in summer 2022. That makes a move to a CL club more likely than signing a new deal with a release clause.
Why can't we replace him? Sure it won't be easy and we have failed to adequately replace players before. But we have also been successful replacing and even upgrading players as well.
28 year old Wilson cost Newcastle £20m under one year ago, his price will now be higher. Why would they sell him so soon to us?
If Ings goes we'll probably sign a young striker and look to develop him.
But we don't play one up front. Our massive up turn in form has been playing 4222 and has been adopted throughout the club, no reason to change that now even if Ings doesn't play.