I think it’s rather optimistic to believe the Epic Games Store going to overtake Steam. If that’s the criteria for raising their cut, I wouldn’t expect it to happen anytime soon. Outside of annoying exclusive distribution rights on some games, having another store has given game developers another way to sell and players a way to purchase games cheaper. With that said, I’d guess their real gambit is to create enough pressure to drive the standard 30% down.
Maybe 30% made sense at one point. Maybe it does now. It strikes me that there have been efficiencies that haven’t been passed along to the consumer. Having a competitive market would let us find out.