My main worry is that in the short term that the games market will fragment into several mutually exclusive launchers, each with a stranglehold on certain content.
TL;DR: That last sentence.
That has been kind of happening for a bit, actually.
I remember heck, when some games were basically on Stardock Impulse. GameStop bought Impulse, when Stardock failed to beat Steam - and well, now their games are on Steam. [shrug]
EA was putting all their stuff over on only Origin, since BF3. They only recently decided to bring some of their older stuff (since BF3) over to Steam, since they probably need more sales.
Even Microsoft, who stopped putting stuff on Steam for a while, is finally back to putting stuff on Steam.
Ubi though...had decided to drop Steam, for the time being.
I'm glad to see Sony planning to bring some of their titles to PC. First the Quantic Dream games (Heavy Rain, Beyond: Two Souls, and Detroit: Become Human) - and now we will be getting Horizon: Zero Dawn. Hoping more come here.
I don't think I really see many - heck, if any games - are actually exclusive to GOG.
We've also been seeing recent Activision titles like say the CoD titles - like Black Ops 4 and COD: MW Reboot - skip Steam entirely and just put their games on Battle.Net.
I don't know if the AAA companies can really afford anymore to really skip out on any platforms anymore, as they will likely...need the $ and sales. They're spending so much on development & marketing - they need these sales. I could see say timed-exclusives becoming more of a thing, though - as games might not be on X service for a time period, but might just come anywhere from 6 months to a few years later, when they really need to make that double-dip $ or need to hit that segment of the audience that they haven't hit yet.