It looks like at some point in the future, Overwatch 1 and Overwatch 2 will merge clients.
According to Kotaku (via PcGamesN), Jeff Kaplan spoke specifically about this merger,
“There will be a point where the clients merge. We think this is important, especially as a competitive experience. The whole idea is to avoid fragmenting the player base and giving anybody a competitive advantage. If we’re playing in the same competitive pool, you’d better not have a better framerate just because you’re on a different version of the engine.”
This was in response to just why content updates for Overwatch 1 have been slow lately,
“Overwatch 2 was 100 percent the reason. And that was the reason that we were so excited to announce Overwatch 2. We now feel like we can have that open dialogue with the community of, ‘This is what we’re doing, this is why we’re doing these things.’”
In case you missed it, all your skins and cosmetics will transfer to the sequel. Overwatch 2 is set to receive PvE content including a new PvP mode called Push.
