PSNow sounds more likely which they do anyway. Epic Games Store and Steam sound likely to be the case here.
I think Sony will follow MS in this case, and release the games that don't sell well on other platforms to increase sales. Why not if a game is not selling well.
Microsoft have changed their tactic, it seems all games will come to Steam now. Halo MCC is launching on it after all, and AOE2:DE when previously AOE:DE didn't. It looks like they've given up on trying to push pc gamers to their terrible Windows store.
Gears 5 is also launching on Steam. So it's not just games that don't sell well for Microsoft. It's all games.