Two year transition, folks; everything across the entire Mac line-up gets Apple Silicon chips...
A Family of chips for the Mac platform...
M1 will be a series; M1, M1X, M1Z, M1whatever...
I could see Apple having four variants of the M1...
So far we have been shown the low-end variant, the M1...
Two more variants, each with increasing performance (and thermal envelope) to cover the laptops/iMacs/mini, and the largest / highest performance for the (smaller) Mac Pro...
And possibly for a 32" iMac Pro based on the XDR display, $999 stand included...
LOL, that would be silly, it would have to be a $10K base model...!!!
Low-end - 13" MacBook Air / 13" MacBook Pro / Mac mini
All Low-end have two USB4 ports, all Low-midrange & up have four USB4 ports...
Low-midrange - Mac mini / 24" iMac / 14" MacBook Pro
High-midrange - 27" iMac / 16" MacBook Pro
High-end - iMac Pro / Mac Pro
The iMac Pro could be any one of the following sizes; 27", 30", or 32" XDR...
But if they do a XDR-based iMac Pro, it for sure better have Target Display Mode (and the ability to then use the internals as a headless server / render node)...!
Low-end - already out
Low-midrange - Q2 2021
High-midrange - Q4 2021 / Q1 2022
High-end - announced Q2 2022 / shipping Q4 2022
Apple will run each generation of M-series APUs for two years, with product stack roll-out very similar to the above outlined transition...!
iPhones / iPads are refreshed every year or 18 months, but they also sell way more, people want the latest & greatest; but Macs are more expensive, and folks are used to making a "computer" last longer than a phone or tablet, so a two year cycle for Apple Silicon Macs...