According to AnandTech, the USB-IF is optimistic that the specification will be finalised by September. That said, the USB 4 specifications was previously expected to be published by the middle of 2019. The spec is currently in version 0.7. On the flip side, the USB-IF believes that devices with USB 4 will be available by the end of 2020.
To quickly recap, USB 4 will be based on Intel’s Thunderbolt 3 interface, but with double the bandwidth. This allows it to perform two lane operations using existing USB-C cables, and up to 40Gbps using cables certified for such speeds. While the publishing of the USB 4 specs looks to be a little behind schedule, it looks like we will see USB 4-supported devices a little earlier than expected. (Source: AnandTech)