Microsoft is really taking their "Game Pass" and "no platform left behind" philosophy to the extreme, it seems.
Although the recent Xbox Games Showcase didn't say this specifically, IGN later confirmed that Halo Infinite was the start of something long term. Studio Head Chris Lee has announced that Infinite is going to be a platform of sorts, hosting content "for the future," with Infinite "growing over time...as the start of the next ten years for Halo and then building that as we go with our fans and community."
343 Industries seems to come out and say that Halo is not going to become Destiny (thank goodness), but the game will get free updates (raytracing is coming at some point). More story content will be added as well, and the numbered sequel convention is a thing of the past: at least at this moment.
Of course, if Infinite's launch doesn't go as planned, things could change and we could get another Halo reboot or a proper sequel that promises to fix what theoretically went wrong. We've seen it a million times before. But for now, Microsoft is all-in on Infinite, and I think that helps its prospects immensely: especially now that four player split-screen co-op is confirmed.