The last PPC (G5) was released in 2003. Snow Leopard dropped support in 2009.
The MP7,1 was released December 2019, so the same support window would be 2025. Equally importantly, the M2 obviously can't be used in a MacPro level machine, and if they stick to only +4 cores for M3 (so 16) or +50% (18 cores) even M3 is unlikely be used in a MacPro. That puts Apple 3 generations away from a replacement product, which obviously is not happening in 2022.
2006 the Intel Mac Pro was released
2007 Leopard was released and the last PowerPC was supported (Universal Binary with Rosetta)
By 2009 Snow Leopard was released and PowerPC code base was completely dropped.
Going by these metrics, like I said, macOS 13 (2022) will
most likely not support Intel at all. You will only get .dot updates in macOS 12 (Whatever it will be called, maybe Monterey, we will find out next week).
By then we will have M2+ chips (there have been rumors of 64 core Mac Pros with ARM chips) and hopefully new Mac Pros that can compete with the overpriced 28 core Intels from 2019. I think Apple can compete with CPUs, but not GPUs, they can't match AMD/NVIDIA yet. So they either open up PCIe lanes in their ARM chips so AMD GPUs can be in addition to their iGPUs, or they just go all in on their SoC.
No one really knows, we waited 7 years for a Mac Pro 7,1, and we can wait another year to see what they are doing.
Anyway to me personally, I tried a M1 Mac Mini and for my workflow it's really useless. I need high thread counts with high performance cores, I don't need H264/H265 hardware encoders that are baked into the SoC.