Halo is moving to Unreal Engine 5. Here’s the topline from 343 but…not 343, as along with this announcement is a rebrand to “Halo Studios”:

Microsoft is moving its Halo development to Unreal Engine 5, after more than a year of rumors of an engine switch following a leadership overhaul at 343 Industries, layoffs, and other changes. 343 Industries is now becoming Halo Studios as part of this engine change announcement, hoping to mark a new chapter in the history of Halo.

It's recently been revealed that the Halo series will be moving to Unreal Engine 5, which may support a long-running franchise rumor.