It will support PCIe 5.0 on the slots directly connected to the CPU, but probably only on X670E motherboards. Note that there will be very few 5.0 devices on the market and you won't be able to notice the performance difference.
My interpretation is that the chipsets wil have PCIEe 5 connections as follows:
X670E: "Everywhere" according to the talk, which I interpret as:
- 16 lanes of pcie 5 to the main pcie slots
- 4 lanes of pcie 5 to the primary nvme slot (i would not be surprised if some boards will expose this as a pcie x 16 slot (with 4 lanes)) though.
- 4 lanes of pcie 5 to the chipset (speculative)
For the regular X670:
- 16+4 pcie5 lanes to "GPU" and "nvme" slots, as for the X670, perhaps only 1 nvme slot, perhaps with an additional nvme x8 slot when running 8/8/4 instead of 16/0/4.
- "only" nvme 4 to the chipset
B570:
- Only the "nvme" slot will have version 5
If I'm right, the Extreme card will offer twice the performance over the chipset, compared to AM4, which could allow it to fill some of the use cases currently covered by the non-pro threadrippers. If I'm wrong, and even the extreme X670E chipset will not be a good choice for those who depend on a lot of IO, compared to threadripper or Intel.
Hopefully, I'm right, and in that case, I'm not sure if we need an intermediate step between the 7950x and lower end threadripper pro setups, at least not for connectivity and I/O. And those who actually need more compute than the 7950x will over will probably not care that much about the price premium of threadripper pro vs regular threadripper.
Saying there are few devices yet on the market is not helpful. You don't buy a PC for the next 6 months. In a 1-2-3 years when your PC will be still ok it is very likely that more PCIe5.0 devices will be out, and probably not compatible with your MB.
I upgrade every couple of years to the best hardware on the market, but even for me PCIe 5 is just “nice to have”. No GPUs support it yet and rumors suggest that RTX40 will also be PCIe 4.
