I've been thinking about this myself. I have some search alerts set and no real hits for a Pro. I'm thinking that next year's Apple Silicon M1X, or M2, or whatever, will be in new MacBook Pros (14/16"), a "pro-ish" Mac mini, and iMacs. But I kinda wonder whether a high-spec'd iMac will be billed as the replacement for iMac Pro. Seems like they might have a yield problem if all next year's macs have new Apple Silicon, so I would not be surrpsied by smaller iMac having M1.
My guess is redesigned iMac will be available first, and later (if at all) an iMac Pro with similar design. The current iMac Pro's cooling design is likley overkill for Apple Silicon, so it would not be used for update. But this is just a hunch. Maybe they'll call the larger iMac model with M2 "iMac Pro."