The upcoming Qualcomm Snapdragon 875 SoC will come with ARM's latest Cortex-X1 and Cortex-A78 cores. The chip's configuration will likely consist of a single Cortex-X1 core coupled with three Cortex-A78 cores and four Cortex A-55 cores. The Snapdragon 875 will be unveiled sometime in Q4 2020, and will reportedly make its debut on a Xiaomi phone.
https://www.notebookcheck.net/Qualcomm-Snapdragon-875-will-be-at-least-30-percent-faster-than-its-predecessor-thanks-to-ARM-s-Cortex-X1-super-core.466907.0.html
This article confuses incomparable figures. X1 has 30% higher integer performance than A77, iso-process, A78 has 20% higher integer than A77, 5nm vs. 7nm.
X1 is in fact 22% faster than A78, iso-process. The takeaway here is that ARM now intends for the A78 to be a specialized mid-core, since it's 36%
more efficient, i.e. consumes 36% less power, at A77's peak performance, while X1 is to be the specialized performance core, or flagship core.