Early last week Apple posted a new Thunderbolt FAQ up on its website. While there isn’t much new information to relay, it’s worth poring over if you’re interested in taking advantage of Apple’s new transfer technology anytime soon and are curious about its functionality.
9. Can I use Target Disk Mode with a Thunderbolt to Thunderbolt cable (2 m) and a third-party storage device that uses Thunderbolt?
Yes. The Thunderbolt logo should appear with the FireWire logo when you start up a Thunderbolt-enabled Mac and have a Thunderbolt storage device connected. If you have both a Thunderbolt and a FireWire storage device connected and enter Target Disk Mode, the Thunderbolt-enabled device will be the default. If you disconnect either a Thunderbolt or FireWire storage device after successfully entering Target Disk Mode, the corresponding icon should disappear from the display.
Check out the entire FAQ here.