If England win the Euro's, and Mason isn't transformed into a central player, I fear he woll have a very tough time being integrated within the squad.
Sterling and Saka will have special credit for their contributions during a historic campaign, whereas Rashford, Grealish, Sancho, Foden are all there as well. I doubt he's get in, in front of any of them.
He might be able to take on Calvert-Lewin, but it would be a shame if he really has to wait for Kane/Sterling to get too old to play.
At the same time, doubt any England fan cares.