be happy as you wish , I am addressing NVME makers not you. millions of people bought their PCs three or two or one years ago and not from 2011 .. and they are a large market share. not to mention that the majority of PCs in the market are intel based and not AMD based. People who prefer intel over AMD are buying their PC as we speak without Gen 4 PCIe.
People who really care about nvme speed difference between pcie4 vs 3 eithe already have pcie4 or are just about to purchase it. So no, there is no large market. I give you that some of the millions of people you mention indeed could possibly care about it, and from some perspective maybe "should" care about it.
But even so, the fact is that the people who
care enough are not a large market share. Neither in absolute terms or even in comparison to, say, LGA 1366 Xeon enthusiasts. Especially if we are talking about those who care enough to pay a sufficient premium to cover the manufacturers' expenses incurring from making two versions of a cutting edge high-tech product. Not to mention within a market that is already highly competitive as is.
So, I am addressing you on behalf of NVME makers here, telling how they would reply. They would reply: "No, we shouldn't."