Whether branded iMac or iMac Pro (or both?) I do think that if it's "only" the same configs as the MBP 14 and 16 Pro/Max chips, then it definitely needs to have a lot of other special sauce e.g. 128GB RAM, 30-32" 6k screen, promotion, etc.
...but that's one of the consequences of Apple Silicon - by delivering midrange-desktop-level performance at laptop-level power consumption it has made the choice more about preferred form-factor than power. That's already shown up with MBPs - the 15/16" Intel had a significantly better CPU and GPU than even the higher-end 13" Now the 14" and 16" have, broadly, the same processor and RAM options and comparable performance - it's much more about what screen size you want.
I think a lot of people would be very happy with a M1 Pro in a re-vamped 27" 5k iMac form-factor. 99% of the computing world are still using 4k, if not 1080p displays so, even though the 5k display is "mature" it is still comfortably ahead of the game and part of what makes the 5k iMac possible Apple's best-value machine - and I'm sure Apple could squeeze in some improvements or a bezel shrink... but if it involves adding $1000 to the price (and claiming it as a bargain c.f. the Pro XDR) then they're risking making the iMac another niche machine.
Most people I know who purchased the iMac Pro were software developers, photo editors and podcasters who purchased it for the power, the quiet and because it had a 5K display. And for them, it was more than powerful enough at those tasks to last them to this day, so they had no incentive to buy an updated model even if had been made available last year.
...well, that's hard to prove when there
was no updated model to buy (and, for the last year, we've known that Apple Silicon was coming Real Soon Now). It's Apple's job to produce products that make people want to upgrade. Also, if they're relying on buyers of $5000 "pro" computers to upgrade every year or two then they're making the mistake of treating pro computers as if they were fashion items like iPhones and Watches (or even lower-end MacBooks). If there
is a cycle it's more like 3-5 years based on equipment leases or the rate at which businesses can claim equipment costs against tax. But then there are all those people with older Macs, or who want to shift to a desktop + iPad model or (heaven forfend) might want to switch from PC who
also need to be offered something exciting and up-to-date, whenever they come along. The iMP was, maybe, a contender in 2017/18 - when the iMP spec was fresh and the top-end iMac less powerful - but Apple did nothing (I think there was a minor spec bump) to keep it current. By 2020, even a regular Core i iMac with the pro's improved cooling system would have been a more attractive product, especially for people who didn't already own an iMP.
Anyway, back to the original point, the price of the iMac Pro was
laughable unless you factored in the premium that Intel, and the whole industry, charges for Xeon/ECC/"Workstation-class" graphics - and even that seems to be partly down to artificial scarcity on Intel's part and a "nobody ever got fired for buying Xeon" mentality in the industry, otherwise AMD would be cleaning up even more than they are. The only way such a distinction will exist in the Apple Silicon world is if Apple go out of their way to try and create one (but they're not going to be able to create the "nobody got fired" aspect of Xeon) - which, unless they have something else up their sleeves - would have to be based on either Jade 2C or 4C. Of course, if they limit the 2C or 4C to the most expensive, lowest selling Macs, they'll only be making them in (relatively) tiny quantities so they
will be hideously expensive. Or, they could use the 2C right across the desktop range and enjoy the economies of scale - including a market for all the dies with up to 40% dead cores and an eye-watering mark-up for the fully functional 20 core version.