I've been sitting on my 2012 Mac Pro and 2011 MBP for 9 and 10 years respectively.
Obviously I fell behind on OS updates years ago.
Been saving and waiting for a replacement for the tower since about 2016. When the 2019 tower came out I was shocked by the price (who wasn't) - $10 000 AU for the baseline model and that was before you even added any RAM or upgraded the 8-core Intel chip.
Now, touch wood, having had the "opportunity" to continue on the savings path and with the new machine, (Q2 next year I'm bettin'), being uber-powerful and at a reasonable price (at the very least not in the realm of the 2019 Intel model), I should be able to replace both the lappy and the tower in one hit.
That was always the goal 'cause my home stereo is the lappy running iTunes and transfer between the two machines has to be seamless, which of course it wouldn't be if the tower was Apple Silicon (Music app) and the lappy an 11-year-old (by then) Intel (iTunes app). Sure, Music will read iTunes libraries, but not the other way around, and migration for me is generally from the tower to the lappy.
Anyone who needs a tower / desktop unit, I implore you to hold out if possible for the AS model/s, which if Apple remains on-target with the prediction made in (May?) 2020, should start to drop during Q2 2022. I predict that they'll not only be by far the most-powerful computers Apple's ever made, but that peeps are going to be blown away by them, and not just Apple geeks.