There are no announced or released Zen 3 mobile CPUs at this time. You are correct in that the Zen 2 mobile CPUs currently top out at 8 cores, and up to about 54W TDP - the top CPU is the "45W" Ryzen 9 4900H which can be configured up to about 54W by the OEM. We might see Zen 3 mobile early in 2021.