Maxing out the 27" iMac (Nano, i9, 128GB, 8TB SSD, 5700XT) lands just south of $9,000.00 USD. This is your one and only warning that the iMac Pro is getting zero updates, buy it at your own risk.
Apple laid the groundwork for this to be either the final Intel iMac or the next to final update as they will be able to simply drop in a Rocket Lake-S CPU using the same 400-Series PCH that is in this model and leave everything else the same. Whether that happens depends on how well uptake of the AplSi goes over the next year. The inclusion of T2 surprises me, but that simply means that those of us without T2 will probably lose macOS updates sooner than those with T2, but I'm rumormongering without solid evidence.
Obviously, by the lack of any meaningful update to the 21.5" 4K iMac, this is the final version of that model. We will be treated to a 23" AplSi iMac in October for the holiday buying season or Apple will hold it until Q1/2021.
Solid upgrade, if uninspired. Anyone thinking Apple would redesign the iMac before the AplSi switch is picking and choosing their delusions.