Thunderbolt has plenty of life left in it, Thunderbolt 3 will eventually be widely adopted over USB-C, and will be backwards compatible (as Thunderbolt 1 is with 2). So the worst case scenario in the medium term is needing a connection hub with Thunderbolt connections for computers which only have USB-C ports (*cough Apple *cough*).
People get hung up on 'speed' and bandwidth, these things are important, but usually not too important for the kinds of recording projects we might undertake, we're mostly bothered about achievable latency and, really, USB 2.0 is more than capable for the relatively small projects (lets say 16 analogue channels simultaneously) we might undertake. If you are someone who presides over orchestra recording (a LOT of channels) or track with a lot of plugins/processing happening, you're the exception .
Si
Focusrite Technical Support