Intel is working on a new Thunderbolt controller that will double the bandwidth to 20Gbps:
The speediest Thunderbolt controller code-named Falcon Ridge will support speeds up to 20Gb/s as well as DisplayPort v1.1a and DisplayPort v1.2 Redriver. The latter technologies will also be supported by the Redwood Ridge controllers due in 2013, reports DigiTimes web-site. Given the fact that now Intel reportedly charges $20 per TB controller, the new ones should be more affordable.
The new - Falcon Ridge - Thunderbolt chip clearly improves speed by implementing PCI Express 3.0 technology outside the PC. From what has been told, it is obvious that it will continue to use copper cables.