They should just have PCIe5 as default.
Why? Adds hugely to price for CPU and mobo, and we cant use it yet.
If its internal between chipset and CPU, they can use it to give us twice as many 4.0 lanes - none of that bullshit with NVME disabling SATA ports, etc.
At a guess, They'd be smart to have the generations planned now based on how AM4 went:
Gen 1: PCI-E 4.0 for all external connections (Use 8x 5.0 CPU-> chipset so that you're not crippled with a 4.0 CPU?) - use that bandwidth for 20/40Gb USB 4.0?
Gen 2: PCI-4.0 everywhere, CPU->chipset 5.0 with GPU and first NVME slot (ala B550)
Gen 3: PCI-E 5.0 everywhere
That would let them plan out designs in advance, and let mobo manfucaturers support various CPU's - we'll have Athlons and APU's with less PCI-E lanes (or even Gen 3.0)
Also possible and logical is the A and B series boards for these generations following that same basic guideline with A/B boards being one gen lower than the X series boards.