That is a good question - for Dell.
You have to ask Dell what processors are supported by their bios. Then, you can select from those.
An upgrade processor must be socket, chipset, and bios compatible.
Immediately obvious steps have been taken.
Still waiting for resolution from Dell, although new 5820's are stated to be available for configuration & purchase with the W-2295 option.
CPU upgrades, sans drama, have been the experience so far - more disruptive/expensive solutions like M/B swap etc., will now open up consideration for alternative CPU/vendor.