Because if they were to make a “WoW2” it would be dead upon arrival.
The reason why WoW is still relevant and in many, many regards still king of MMOs is because it is WoW. 20 years old with design elements that no longer works in modern MMOs. It works because of its reputation as World of Warcraft. Every other game that has tried to mimic that has failed catastrophically!
If WoW were to be discontinued for a WoW 2 then… why not play another modern MMO already? Why not go elsewhere?
World of Warcraft is aging and that’s the only way folks will truly stop playing the game. And even then, when it is long past it’s time, it’ll be possible to make money from the game by re-releasing content through Classic, to re-imagine it again … as is currently happening. WoW is king because of its name and age, deleting that to try to capture an audience that isn’t and will never be interested in WoW is a losing proposition.
It is entirely possible that down the road we’ll get other games set in the Warcraft universe, but we will never see a WoW2. Maybe one day the engine gets completely overhauled and we see some of the modern concepts more realized in game, and maybe then it receives the nickname of WoW 2 Electric Boogaloo. But there won’t ever be a World of Warcraft 2 in any official capacity.
To think anything else is just a dream, and also most likely a nightmare.