Future AMD processors could be coming with USB4 support and DisplayPort tunneling sometime soon. According to Phoronix, AMD Linux driver engineers are working on a new AMDGPU kernel graphics driver featuring initial support for USB4 DisplayPort tunneling technology.
We don't know exactly what architecture will come with USB4, however, rumors are floating around that AMD's Ryzen 6000 series APUs codenamed "Yellow Carp" and "Rembrandt" could feature USB4 connectivity. If so, then AMD will likely be targeting laptops for USB4 adoption first before bringing it over to desktop Ryzen-based CPUs and Radeon RDNA-based graphics cards.
Tunneling is a new feature introduced to USB4 that comes from the port's Thunderbolt 3 integration. Tunneling allows multiple protocols, including USB, DisplayPort and PCIe, to all operate at the same time (albeit with reduced bandwidth per protocol). This is different from USB alt mode, which allows only a single protocol to be active at a time.
Alt mode can still be useful if you need all of your USB bandwidth targeted towards one protocol, however, tunneling could prove to be more advantageous when you don't need all bandwidth targeted towards one connection (like a USB dock with multiple ports).
The new AMDGPU kernel graphics driver is almost ready to be delivered to the public, and according to Phoronix, could be ready in time for Linux 5.16. This could very well mean that AMD is preparing USB 4 support for its next generation of CPUs or GPUs.