Your analysis is based on the assumption that Thunderbolt is only used for copying data from a single drive. This is just silly.
1. Daisy chain devices
2. Copy to and from very fast RAID arrays
3. Drive displays
4. Drive external GPUs
And probably lots of other stuff I couldn't think of off the top of my head.
Ok then, thanks for the information. Let's see if they actually start making more devices fitted with Thunderbolt.