Apple seems to be in the process of dismantling the iMac Pro, with the store page for the advanced all-in-one Mac, including a “While supplies last”, and only the base model without custom configurations available for purchase.
IMac Pro was launched in December 2017, and while there have been a few adjustments to the available configurations over the years, it has not received any significant hardware updates in its lifetime. As a result, we have for some time recommended that users do not purchase the iMac Pro as an advanced standard iMac currently provides better value.
There have been some rumors of an updated iMac Pro over the years, including from analyst Ming-Chi Kuo almost exactly one year ago.
It is unclear whether the iMac Pro will be phased out completely, or whether Apple will sell through existing stock before an update, but the unusual note about failing supplies suggests that the computer may indeed be on the verge of complete decommissioning. If an updated version arrives, it seems that it may not be ready for launch for a while yet, and there may be a gap in availability when the current model is sold out.