Bungie could cease the addition of expansions to Destiny 2 to focus on Destiny 3, but they also might not - it all depends on the feedback they get from players.
Destiny 2 took quite a while to earn respect after failing to live up to the franchise legacy plotted by the first game, but it's finally in a good place, although there was some recent backlash over the nerfing of multiple weapons.
Bungie recently announced the upcoming Shadowkeep expansion for the game's third year but they claim that year four will depend on fan reaction.
"We try to plan for multiple future universes," creative chief Mark Noseworthy told Kotaku in an interview. "And like, ‘Hey if this happens we go to the left, if this happens we go down the middle, if this happens we go to the right—what are the commonalities between all of those?’
"That’s a burden that I think most of the senior leaders on the project have to carry, this incredible ambiguity. We try as much as we can to not infect the team with that kind of poison, because it’s just devastating to velocity and your understanding of, ‘Oh are we making an expansion next year or are we not? I dunno, what am I even working on?’
"That’s one of the hardest parts of running a live game service like this is just not having that perfect crystal ball, and the team wants it. The more certainty and track we can lay down in front of them, the better the experiences they’re going to build... We have a plan and we think it’s pretty good and we’re going to find out from our players if it’s really good or if we need a new plan."
So, in a nutshell, Bungie has no idea what they're going to do as it pertains to the Destiny franchise. They're going to play it by ear and whatever path they opt to go down will be contingent on the feedback they receive from players.
The developers could be credited for their attempt at total transparency, if anything, but we imagine whatever they choose to do will be well received as it will likely be the course the majority of fans want them to take.