They might bump the specs for the refresh, but hard to say. The 8,1 may or may not be coming this year based on what tsialex said about the supply chain issues.
Again, I don't have any info on the specifics of the 2019 Mac Pro supply chain. I track the semiconductor market news and the supply chain issues for PMICs started happening since at least the second half of 2019, the pandemic aggravated it and now it's impossible to source. GPUs were greatly affect by it too, lot's of power ICs on the GPU PCBs. PS5, cars…
Apple usually contract with firm orders, even paying in advance, what will be needed for a production run. Since Mac Pro 2019 probably was a interim low scale product that would have a refresh when the substitute of the Skylake Xeon was available, Apple contracted what they thought that was needed with some margin for the availability of repairs, but Intel delayed Ice Lake and then the pandemic happened. By now, Apple probably used all of the contracted components and even the reserve/spares for the expected repairs and now we are in a unforeseen situation - without the refresh for the 2019 Mac Pro and can't even buy the 2019 model without having to wait two months.
Hardware designers are changing designs since at least the end of 2020 to lessen the dependence on unobtainium power CIs. This is also happening with some microcontrollers, some hardware designers that I follow on Twitter even went back to DIP/thru-hole chips from the late 90's/early 2000s to have some availability of components and keep products on the shelves - for example, the STM32 family of microcontrollers are not available for a year now. Some are even designing PCBs that could work with different types of chip encapsulation or even alternate chips, just to keep the production going.
Anyone that have a product with a strict BOM is having lot's of headaches for at least a year by now.
