[…]Today, Intel announced that it contributed the Intel Thunderbolt protocol specification to the USB Promoter Group, enabling other chip makers to build Thunderbolt compatible silicon, royalty-free. In addition, the USB Promoter Group announced the pending release of the USB4 specification, based on the Thunderbolt protocol. […]
https://newsroom.intel.com/news/intel-takes-steps-enable-thunderbolt-3-everywhere-releases-protocol/
https://betanews.com/2019/03/04/usb-usb4-four-universal-serial-bus/
https://techcrunch.com/2019/03/04/with-usb-4-thunderbolt-and-usb-will-converge/