Reviews thus far have shown the difference between PCIe3 and PCIe4 to be rather inconsequential. While I initially thought Rocket Lake with PCie4 would be of interest, if Alder Lake with PCIe5 and DDR5 is coming in second half of 2021, that seems like the better upgrade path for me from my 9600k. Hopefully the Nvidia 4000 GPU series will be able to take advantage of PCIe5. 24 lanes would also be nice so that eight could be used for two NVMe drives and still have full 16 available for the graphics card.
The reason PCIe 4.0 doesn't tend to make much of a difference over PCIe 3.0 for today's graphics cards is that PCIe 3.0 is already providing enough bandwidth, so the additional bandwidth of PCIe 4.0 isn't being utilized. Adding even more bandwidth on top of that isn't going to help, and I would expect the performance to be more or less identical to the PCIe 4.0 numbers for any graphics cards released in the near-future. As such, I doubt we will be seeing PCIe 5.0 on consumer platforms for some years to come, as it would just increase motherboard costs without providing significant benefits. More lanes for things like storage could be nice, but there's no reason why Intel or AMD couldn't do that on PCIe 4.0 or 3.0 consumer boards if they really wanted to.
DDR5 could potentially make an appearance on some consumer motherboards in 2022, or perhaps late 2021, but it might not be substantially faster than DDR4 initially, and will probably cost a lot more.