New optimization discoveries were made with USB 2.0 drivers years ago. Even Metric Halo, makers of the first FireWire audio interface for OS X, and known for their future proof hardware model, are moving toward USB.
But I have to ask why would latency be an issue when you have hardware monitoring via the mixer on the way in? Do you plan on doing lots of overdubs?
You might be interested in checking the Gearslutz thread which offers details on drivers, latency, and converter technology borrowed from other SoundCraft and Harmon product lines.