I cannot imagine they would skip the battle.net launcher, but I would love it if they did!
EDIT:
Players using Steam will have access to features of the platform while playing Overwatch 2, such as Steam achievements, their Steam friends list, and the ability to invite them to play in-game.
Not to sound doom gloomy here, but my reasons for ditching Blizzard games were absolutely not the launcher. I don't think I'll be going back to Overwatch or anything else in their portfolio because of my issues with game development/marketing (PvE in OW2 promises vs. reality, Warcraft 3 Reforged debacle, etc.).
That said, for anyone who still is up on Blizzard properties, having platform choice is always nice. I still play a ton of Apex Legends and love that it's available via Steam rather than just EA's launcher, for example.
I'm not fond of blizzard and I think overwatch 2's time has long since passed so I'm not sure how helpful this will be
But I still play hearthstone and I sincerely think that it's the best the game has ever been so hopefully a steam release is a second wind for the game. Not that it's dead by any means but I'd love for it to feel like a popular game again