This is despite the fact that PCI-SIG has only recently completed its work on PCIe 5.0, which will have double the bandwidth of PCIe 4.0 at 128GB/s. With PCIe 6.0, that bandwidth is doubled yet again, meaning that motherboard in the year 2021 will be sporting PCIe bandwidths of 256GB/s. As explained by PCI-SIG, the group plans on attaining this high bandwidth speed via two specification updates. The first is the quad-level Pulse Amplitude Modulation (PAM-4), while the other update is something called Low Latency Forward Error Correction (FEC) feature.
Finalising a new PCIe standard takes years, but as we mentioned, at least it is on the right track. At it stands, PCIe 4.0 has so far only been adopted by AMD and its respective Zen2 CPU and Radeon Navi GPU architectures. Namely, its AMD Ryzen 3000 series and Radeon RX 5000 series graphics cards. Even more exciting is that by the time PCIe 6.0 makes it to the market, both AMD and NVIDIA would have released newer and more powerful graphics card, accommodating the new interface. (Source: PCI-SIG via Techspot, Hot Hardware)