With the massive success that Fortnite and PlayerUnknown's Battlegrounds have been seeing, many other developers have been latching onto the Battle Royale idea. Established franchises like Call of Duty and Battlefield are now adding Battle Royale modes to their upcoming titles. But 343 Industries, the current team manning the Halo franchise, has no interest in bringing Master Chief into the hot genre.
In a recent stream on Mixer, James Bachici and Jeff Easterling of 343 stated that "the only BR [they're] really interested in is Battle Rifle." So while EA and Activision made a big to-do at E3 about their foray into Battle Royale, 343 is much more interested in bringing Halo back to its roots.
The next game in the franchise, Halo Infinite, is taking a lot of criticism to heart and trying to fix a lot of the problems people had with Halo 5: Guardians. Most notably, Master Chief will be back as the focal point of the story and the art direction will be much more in-line with what was seen during Bungie's original trilogy. While 343's Halo titles have gotten good reviews and have broken sales records, most reviewers feel that 343 has yet to recapture the original titles' lightning-in-a-bottle feel, so it's probably for the best that they're trying to turn Halo into back into Halo and not a big budget Fortnite.
Halo Infinite does not have a true launch date yet, but many are expecting it to be released within the next year.