Overwatch 2 will absorb the original Overwatch client
They don't want to fragment the gaming community. At its core, Overwatch 2 is like a paid expansion but is sold as a sequel.
Overwatch 2 is an odd case. It's a sequel because it has "2" in the title as Blizzard is selling it, but it looks like it's actually an expansion. It's still early in its development cycle, so not many details have been revealed yet, but it is known that all of the heroes, maps, modes, and cosmetics coming to Overwatch 2 will also be playable in the original game. Jeff Kaplan has said that his goal is to one day bring both games together in a single Battle.net client.
The original Overwatch will disappear when the sequel is out
According to Kaplan, there will be a point where customers merge. They believe this is important, especially as a competitive experience to avoid fragmenting the player base. He gave an example that if we are playing in the same competitive group, it would be better if no one has a better frame rate just because they are on a different version of the engine.
The plan to merge the clients could stem, at least in part, from a desire to protect the integrity of the Overwatch League, the eSports league that is being sold to us so much. But Kaplan said the priority is ensuring players don't end up feeling abandoned as the game evolves.
Kaplan cited the end of an online service as an example: “ We’ve all seen when the servers shut down for game X, Y, or Z. It’s always a story. I always remember the Halo 2 players who just wouldn’t log off. They just kept playing. I thought it was incredible. I wish I had been one of them .” Finally, he said that the launch of Overwatch 2 will allow the developers to continue with the games-as-a-service model with updates and new content, but the original game will receive some significant updates before the sequel or expansion arrives.
Source: PC Gamer