assuming the distribution of app store devs follows a usual power law, this will impact a large number of devs whose revenue makes up a small percent of apple's total take from the app store. 80/20, 90/10, whatever it may be. so id guess their actual revenue hit is probably 5-10% in this specific category. great sounding relative numbers but not much in absolute values.
they'll also play the other side and use the great sounding absolute numbers - ex: "We cut app store commissions in half for over a million small businesses, helping to stimulate the economy in these tough, unprecedented times".
disclaimer: no one expects apple to be a charity, they created and own the app store, their platform their rules, etc. all fine and good but as others have mentioned, without antitrust scrutiny the chances of this happening are far slimmer.