343 Industries are dedicated to making Halo Infinite the "platform for the future" and the "start of the next 10 years" for the Halo franchise, rather than simply another sequel.
Speaking to IGN, 343's Chris Lee stated that they wanted the game to "grow over time," rather than sticking with the traditional numbered sequel releases of old. This sounds more like a continually supported and updated game along the lines of Destiny 2, rather than a traditional Halo game.
It’s really about creating Halo Infinite as the start of the next ten years for Halo and then building that as we go with our fans and community.
Lee went on to state that the team sees Infinite as a "platform for the future" of Halo, but wasn't specific about what that means. It could also be that the engine the game is built on could also be the framework for future releases, however, from the sounds of things, Halo Infinite will be supported for many numbers of years.
There's no release date for the game yet, but it's expected Holiday this year, so hopefully, we'll learn more about what all this means in the near future.