Ok, yes, I know this article is months old, but it's something I just thought of when I noticed my slots were x8/x8 since I installed my second NVMe drive in my second PCIe slot. If top end Navi is the same or greater power than the 2080Ti, it's going to cause a small but measurable performance loss in a slot running at 3.0 x8. Yes Ryzen 3000 and the 500 series chipsets are supposed to be PCIe 4.0 which will be quite sufficient, but for those of us running PCIe 3.0 motherboards, especially first generation Ryzen, it's something to keep in the back of your mind, although PCIe 4.0 May Come To ALL Socket AM4 Boards (at least one slot) may also mitigate this for those of us running first or second gen Ryzen boards. Intel folks are not as lucky.
https://www.techpowerup.com/reviews/NVIDIA/GeForce_RTX_2080_Ti_PCI-Express_Scaling/
