It looks like Halo Infinite developer 343 Industries might be abandoning its custom Slipspace Engine for Unreal Engine.
This comes from journalist Jeremy Penter (thanks VGC), who wrote yesterday (October 2), "I can only confirm that many sources are saying this and very clear that it's already been decided and Halo is for sure switching to Unreal. I feel like it's time for other switches behind the scenes including people leaving and their past problems. Unreal is a great choice."
It's not uncommon for developers to switch engines if they find it isn't working particularly well, like when Kingdom Hearts 3 switched from Square Enix's quite at-the-time broken Luminous Engine to Unreal Engine 4. The awkward thing is that this engine was meant to power the future of the Halo series, which if the reports are true, clearly isn't something it will be doing.
Halo Infinite obviously had quite a rocky time, having been delayed by over a year, arriving last year with missing modes and features such as campaign co-op and the Forge. A roadmap has outlined the arrival of the Forge and campaign co-op for this November, but even that comes with the caveat that split-screen co-op has been cancelled, a staple of the series.
Infinite did have the biggest launch in the series' history, but the inconsistent updates have frustrated players, and numerous staff exits also wouldn't have done any favours for the team's workflow.
There are rumours that a battle royale project is in the works at Halo support developer Certain Affinity, but who knows if that will be enough to restore players faith in the online Halo scene. These rumours haven't mentioned whether this supposed project will be developed in Slipspace or not, but with 343's supposed move to Unreal, it's likely the engine will be left behind for future Halo projects.