ARM is projecting up to 30% increased performance gains over the Cortex-X1 cores by the time the Makalu generation releases in 2022. The Matterhorn generation will introduce improved security features like Memory Tagging Extension, while Makalu is said to be the first generation to support only 64-bit instruction sets.
https://www.notebookcheck.net/ARM-unveils-Matterhorn-and-64-bit-only-Makalu-Cortex-A-cores-scheduled-for-2021-and-2022-respectively.497366.0.html