I don't even understand where all this M#X rumors come from. Why wouldn't the next processor just be M2?
Main reason is Apple's "AX" series of SoCs for the iPad Pro line (2015-2020) that added additional CPU and GPU cores.
Per Bloomberg, Apple is said to be working on an M-series SoC for at least the 14" and 16" MacBook Pro with more CPU cores (8 performance and 2 efficiency) and more GPU cores (16 and 32) under the "JadeC" family codename (which maps to an earlier report from
The China Times stating that the codename for a "prosumer" version of the M1 SoC was "Mount Jade").
So from a marketing standpoint, calling the "JadeC" SoCs as "M1X" would make sense as they would be more powerful versions of the M1 SoC.
"M2" is expected to use the A15 foundation and would be the next generation SoC for the next generation of MacBook Air, 24" iMac and the 13.3" MacBook Pro (if it continues to exist past the current model). Then that would get the "M2X" treatment with more CPU and GPU cores for the more powerful Macs at a later date.