The USB Implementers Forum has published the USB4 specification after months feedback. The new rules, first announced in March, essentially make the latest iteration of the Universal Serial Bus standard almost exactly like Intel's Thunderbolt 3 standard, which the company itself has volunteered for codification.
USB4 will keep the Type-C connector and handle charging based on Power Delivery requirements. However, it will double two-lane data throughput to 40Gbps on certified cables, allow for multiple display link-ups — up to two simultaneous 4K 60fps feeds — and PCIe support for external GPUs. It will remain backwards-compatible with USB 3.2 (including USB 3.1 Gen 1, USB 3.1 Gen 2, USB 3.1, and USB 3.0) and USB 2.0 products as well as being essentially cross-compatible with Thunderbolt 3 devices.
Manufacturers using USB will be able to learn more about the standard in upcoming USB Developer Days conferences through the fall, but we're likely only going to see true USB4 devices starting later on in 2020 at the very earliest.
Source: Speed classes will have confusing names
TechRepublic is hearing from an engineer familiar with the final USB4 standard that speeds will be classed on at least two tiers with throughput of either 20Gbps or 40Gbps distributed to two lanes. As such, the USB-IF will title each class as USB4 Gen 2x2 and USB4 Gen 3x2, respectively — similar to how USB 3.2 Gen 2x2 and USB 3.2 Gen 1x2 were used to describe 20Gbps and 10Gbps throughput.