Again, an RTX 4090 only suffers a 2% performance loss when used on a PCIe 3.0 x16 slot.
What possible consumer oriented product is going to saturate a PCIe 5.0 x16 slot?
Just because it exists in the server market, it doesn't mean it has to be used at the consumer level.
It's like SAS, RDIMM, etc.
I'm not saying it's going to be needed now, or next year, or the year after, but it's the next generation of a standard that is widely, widely used at the consumer level, and there's also been a trend towards running smaller links at higher speeds rather than increasing the number of lanes that CPUs make available and that devices can utilize. One product totally saturating a 5.0 x16 link is unlikely, but if the link is split x8/x4/x4 and is dropping to an older version and also cutting the link width shared among those three devcies to x8, that might be something to watch how well future devices handle. Not an immediate concern, but a trend to possibly keep an eye on.
SAS existed more in parallel to SATA, and RDIMM has been a variant on each version of DDR instead of a direct successor.
Saying that PCIe 6.0 and beyond won't be used on the consumer level means we've either reached the end state for client computing, or we're gonna have to brace ourselves for a compatability-breaking change.