That's a leap. EA sucks. There are plenty of games out there and there are plenty ways of managing them better than steam. Especially if you know your way around a PC.
It'd be another big player, it's not going to be some indie startup that suddenly breaks out into the light to dazzle everyone. And all the other players in this space have their own, worse, storefront and launchers...
Just imagine uplay, but with steam/valves loyal userbase and therefore everyone else sold their games on it. shudders
I mean, who cares? Like having 15 launchers is not a real thing for most gamers I know. It's saved in a cloud server under your profile. Just uninstall after you're done with a game.
You don't even need one for GOG - GOG Galaxy is totally optional and you can download absolutelly run of the mill offline installers for all games on GOG which do not require the installer or any network access, and you even keep the forever and ever (so all your old games are still installable and run on an old gaming computer with the old OS, so long as the hardware hasn't died).