The new M1 mini shows me firsthand what the new Macs will likely be capable of. If the next iMac exceeds what I could build for around $1500, I'll buy one, get Applecare for 3 years, and then sell it for 75% of what I paid for it. Rinse repeat.
For true pro users, I'm confident that the M1 Mac Pro will run rings around the current model at the same price w/ similar configuration.
Upgrading storage is not a major concern w/ thunderbolt ports available. The only upgrade concern for me is RAM. Well that and being unable to find a mid/top tier GPU @ MSRP right now.
Besides my new Mac Mini, I built intel 10900 & 9700k x86 systems this month. I'll see in a couple of years, how things shake out. I don't expect to invest in much other new PC internal hardware during what I see as a transition period.
IMO, the future is ARM or something else even better. Intel & AMD will need to adapt to survive long term in the PC market 5-10 years from now.