That has been the case some what for many years. It takes at least two generation for the GPU bandwidth usage to catch up. And may be we are finally arriving at a plateau with PCIe 5.0 x8 and x16.
So next gen GPU could work with PCIe 6.0 x8 instead. We are looking at PCIe 7.0 devices hopefully by 2029. Plenty of headroom, possibly cost reduction as well.
Purely in terms of BOM, both on the GPU and packaging. Saving Die Space, PCB, Less lane, less testing etc. However the actual cost of implementing PCIe 6 and 7 will be also higher so both will likely cancel out.
So next gen GPU could work with PCIe 6.0 x8 instead. We are looking at PCIe 7.0 devices hopefully by 2029. Plenty of headroom, possibly cost reduction as well.