[Timo]

Firewire's on its way out (try buy a laptop with one now, or even a desktop PC, your choice is very limited).

USB is a stalwart and here to stay. USB v3 is fully back compatible with earlier versions. USB v3 is also forward-compatible, allowing USB v3 devices to be used on older USB v2 ports (albeit at USB v2 speeds).

Thunderbolt is still seemingly fairly elusive, unless you're using Apple stuff, otherwise it's still not mainstream, a niche market.

All comes down to cost. Firewire was technically superior to USB, but firewire was deemed a premium product and USB won the battle overall because of cost - the lower cost of both the interfaces and separate devices. Again, Thunderbolt is superior to USB v3, but USB will win again, due to cost and relevancy to the userbase. If you need speeds that require Thunderbolt, odds on your usage is deemed a 'niche' thing compared to average people's usage.

For relevancy, compatibility and cost, USB is still the best bet to target most users as possible. If Access need more bandwidth, then a USB v2 HighSpeed chipset is needed (instead of the Full Speed chipset they've used in the TIs), or USB v3.