Huge?
The difference between 8x and 16x for gaming is at best 1% but more like 0%.
http://www.gamersnexus.net/guides/2488-pci-e-3-x8-vs-x16-performance-impact-on-gpus
So no even in the future it makes no sense.
Secondly- even in theoretical world where 16x even mattered witch it dont - the number of user using more than 2 gpu and one pci ssd is next to zero. Well. Not that it matters anyway. There is not a tiny bit of performance to get here. Get ram with one cycle less latency and you get more performance in gaming than that.
"Inconsequential Differences & Margins for Error
These numbers are close enough in some instances – like the GTA V 58.3 vs. 58 FPS output – that they're effectively within margin of test error and do not definitively show a performance gap. When a reasonable performance gap is shown – like the ~1% difference in Metro: Last Light numbers – it is imperceptible to the user but measurable with our tools. And we do mean imperceptible – we're talking 96FPS vs. 95FPS, for Metro.
Metro, by the way, is the most reliable FPS benchmarking tool we have ever used. The game produces almost precisely the same AVG, 1% low, and 0.1% lows with every single test pass, and so we trust these metrics as being outside of test variance.
"