You can use contactless payment on Oyster card readers so I don't think they will be missing out.
When I think about it actually, oyster is a quicker method than even apple pay, there is no confirmation or waiting for thumb presses. You just swipe and that's it you go through the gate! Apple couldn't use the apple pay system it would cause too much waiting around and congestion, shame. I suppose they might invent a special implementation of it for use underground with no mobile reception etc and no confirmation.
Maybe apple pay could select the card to use as a digital version of the Oyster card automatically so that it doesn't require confirmation? Hmmm it's a puzzler.