Thunderbolt is marketed as being for fast data transfer to external disk drives, about twice as fast as USB 3, which is several times as fast as most external disk drives. Thunderbold also contains a video cable for Display, which is separate but packaged together.
I think Canon will wait and see, USB 3 is gaining traction and appearing in many new computers, so it would be far more useful in the next few years. HDMI may be replaced by Display Port, but so far, Monitors and TV sets are not rapidly switching to Display Port. Display port can drive DVI and HDMI with a simple adapter, so its quite doable.
