It sure could be, but I'll be shocked if they have their current M1 in the $999 MacBookAir and something still called "M1(x)" in the Mac Pro that has 128+ cores and >128GB RAM, etc. etc.
IMO, that's a totally different product, and it needs a different naming convention. But I'm just guessing.
I suspect M stands for Mac, but it's fair to note that the Mini (and iMac) were using mobile (laptop) hardware previously, so it's certainly plausible that M stands for mobile.
IMO, that's a totally different product, and it needs a different naming convention. But I'm just guessing.