Cycles X was one of the reasons for the delay in the Blender 3.0 release to allow time for this Cycles overhaul to land. As of yesterday, the Cycles-X branch was merged into the Blender 3.0 code-base as a major renderer update.
The merge notes, " This includes much improved GPU rendering performance, viewport interactivity, new shadow catcher, revamped sampling settings, subsurface scattering anisotropy, new GPU volume sampling, improved PMJ sampling pattern, and more. "
While this does bring big GPU performance improvements, at the moment it's limited to NVIDIA GPUs with the OptiX and CUDA back-ends. The OpenCL back-end was removed in Cycles X due to OpenCL being rather stagnate and problems in the Blender back-end support, but Blender developers are working on alternatives for supporting Intel and AMD GPU acceleration too.
In fact, opened yesterday is a merge request adding AMD HIP support to Cycles X. HIP is the interface for Radeon GPUs similar to CUDA. The Cycles X HIP support is still in development and not considered ready for end-users yet.
The updated Blender 3.0 Cycles release notes outline with Cycles X the OptiX kernel compilation time is now significantly lower, baking now supports hardware ray-tracing with OptiX, and a run-through of all the other renderer improvements.
This Cycles X support can be found now in the newest Blender 3.0 daily builds .
Blender 3.0 plans tomorrow to move into its improvement/stability "Bcon2" phase and to run until 20 October when it will turn to bug-fixing-only and code branching. The plan is to officially release Blender 3.0 around 3 December.