Not to sure… Epic would have to compete with the biggest online game seller!
I would welcome it if they did it for sure… But could they do it? Or will they just publish some games to all platforms like they used to? (if they even to anything.)
And there are other competitors… GOG, Origon, that ubisoft thing? Competition is stiff.
But a Steam Killer I do not believe it to be. (Sadly… But I really should stop being so pessimistic! 
)