So what? The point was that when Apple first said they would transition the entire range, 5k iMacs and iMac Pros were part of that range and they've been dropped rather than transitioned to AS. A Mac Studio + Studio Display combo isn't an AS iMac.... YMMV whether you think it's better or worse but it's not a direct replacement.
Pragmatically, The iMac Pro got subsumed by the 2020 5k iMac. Once Intel 'desktop' CPU processor packages went to 8 (and up) cores the iMac Pro was on slippery slope (regardless of Intel -> AS transition). That Intel screwed up the W-2x00 transition from 2100 to 2200 series only greased the slope with even bigger dose of WD-40. Apple didn't immediately lop off sales, but they didn't do anything to stop that subsumption either. Given pandemic supply chain disruptions, that is not all that surprising. They let parts they could readily get, slowly die off to fill the gaps.
The iMac was replaced. Apple explicitly said so. Mac Studio + Studio Display not being a replacement is a 'form over function' argument. The Mac Studio is playing essentially the same role in the Mac product line up as the iMac 27" did. Functionality wise, it is a an extremely viable replacement in most contexts. If you want a "All-in-one" just buy a VESA bracket Studio display and buy a stand that can attach the Studio to. Not going to get a blessing from Apple's 'thinness design politburo' but it would be 'all-in-one'.
The 'iPad on a stick' iMac design path and the iMac Pro are two diverging design concepts. If the 'thinness' folks have taken over the steering wheel of the iMac, then the old 'iMac Pro' concept of pushing the higher AIO thermal envelopes is probably done. It has little to do with Apple Silicon and more to do what road the industrial design folks are driving down. There is no iMac Mn Pro ( or Mn Max) path either if the main logic board has to be stuffed into the narrowest bezel , chin possible to best approximate the iPad features.
The 'iMac on a stick' isn't strictly a direct replacement either. Don't even get a Ethernet socket by default on the entry model. Even if do, it is stuffed into an odd-ball, afterthought location. If Apple has stuffed just only an M1 into a dramatically thinned out 27" iMac (e.g., basically shipped Studio Display with a M1 instead of an A13), then that really wouldn't have been a real direct replacement either. Yes, you can pay even more money to get the Ethernet port and a decent minimum number of ports back... but largely the same thing with the Studio+Studio situation also... just pay more money.
The Mac Mini , MBA , MBP 13" all leveraged repurposed chassis to launch and the iMac 24" drove out into iPad-land. ... Tossing a M1 Pro , Max , and probably even an Ultra wouldn't have been that hard if they simply just reused the iMac Pro chassi. They didn't. There is evidence that Apple was throwing away the classi iMac chassis. And likely painted themselves into a corner on the big screen version.
I believe the statement at the end of the Mac Studio launch was something like "That just leaves one system to transition - the Mac Pro - but that's for another day". Translated: there might be an AS Mac Pro but there certainly ain't gonna be an AS 5k iMac in the immediate future...
That is an entirely contrived interpretation. "leaves one system to be transition" pretty overly implies that it is going to be transitioned. If it not going to be transitioned then why use that descriptive verb?
and there are very clear reasons why Apple might not produce a new high-end iMac: a lot of customers who previously had an Intel MBP for portability and an iMac for power can now get all the power they need from an Apple Silicon MBP with a large screen, which will decimate the iMac market, while people who do want desktop systems will want to choose the display that suits there purposes - and even Apple already offer a choice of two displays. Much more sensible to make a range of laptops, headless desktops and displays which will work with either.
I think a major contributing reason is much more basic than that. The pragmatically proprietary 5K display only worked at the lower price point that Apple was willing to pay because they drove (herded ) so much volume to the component for a relatively long period of time. ( In year one Apple could price those displays at their year 3 rate because had super long commitments to buy for 3+ years, so just got discounts up front since production line was not going to change at all (no screen upgrades) for a very long period of time).
What Apple wants to commit to at 27" at this point in time is likely in flux. The Studio is using a partially tweaked version the legacy screen , but it probably isn't going to be extremely competitive over next 3 years to what will come out in the general market. microLED is still more expensive than Apple wants to pay at class iMac 27" screen prices. Double layer OLED not looking as affordable either. Neither is miniLED. So if going to do a price hike... might as well loop it in as a docking station Display.
Pretty good chance the 24" iMac drifts aimlessly until they figure out 'next gen to commit to for 3-6 years' at an acceptable price point too.
Screen panel tech is going through an evolutionarily burst of activity now and they runs counter to the iMac's need to a long term , cheaper screen component costs. The current 24" screen may drifted into the same catagory as the 'educational iMac' ... long term system on ancient tech (that gets cheaper over time) that doesn't try to keep up on performance at all. Would be totally unsurprising if it fell back to just the limited 2 port model when pushed into the "bargain iMac' mode. There never was a 'edu 27" iMac".
The screen technology transition is playing as big a role as the Apple Silicon one... and it isn't on some explicit deadline that Apple set ( which is even more reasonable move by Apple to map out for the panademic supply chain disruptions. I doubt in 2020 they knew which way they were going to go in 2023-24. They had some 2018-2019 but they had been all shot-to-crap. )