I submit as counter evidence the masts that high frequency traders want to build in Kent, UK. I believe the point is that they can replace some of the fibre in the link between London and Frankfurt with radio, which has a higher speed of light.

http://uk.businessinsider.com/plans-for-high-frequency-tradi...

I also reckon that a modern router can forward a packet in a microsecond. Once you don't involve software in the data plane, routing a packet should only take a few clock cycles.