Halo Infinite was released back in 2021, and it seems like 343 started the development of a new game in the long running series shortly afterwards. As noted by Idle Sloth on X, the former 343 Industries art director Justin Dinges writes in his LinkedIn profile that he was working on "Halo's next unannounced release" between April 2022 and March 2023.
Interestingly enough, the 343 Industries' senior character systems designer Ian Slutz writes on his LinkedIn that he has been "Building player systems and assets in Unreal Engine 5", showing that 343 at least to some extent has moved to the latest version of Epic's graphic engine. If these two projects are related is currently unknown, but we know that Certain Affinity is currently working on a Halo project of their own, which is rumored to be at least somewhat based on battle royale and is also using Unreal Engine 5.
This could mean that 343 Industries has now decided to move away from their own Slipspace Engine, and that Master Chief's future adventures will be developed with Unreal Engine instead.
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