It looks like the bigger iMacs will get optional bigger CPUs. I haven't heard about the Mini, but it has space and thermals to spare after ditching x86 space heaters, so an M1 Pro or M1 Max would still fit neatly.

As for the MacPro, my guess is Apple will keep the chip count to one, but add more performance cores while moving some accelerators outside the CPU package. Video encoders/decoders aren't as bandwidth-hungry as GPUs.