Currently, only the new Sigma lenses from the Art, Contemporary and Sports product series are compatible with the USB dock. The AF of the former two can be adjusted with the dock and the firmware can be updated. With the Sports lenses you can additionally adjust the AF (fast but less precise vs. precise but slower), set a focus limit (which distance range is to be skipped by the AF?) and optimize the image stabilizer’s mode of operation according to one’s own needs. If rumor-sites such as Photo-Rumors.com and Sigma-Rumors.com are to be believed, Sigma diligently works on making the dock compatible for older lenses as well.
Which older lenses will be made compatible with the dock and when exactly the firmware update will be released is yet unknown. I can imagine that only the newer EX or HSM/OS glass fulfills the hardware requirements. Also, it is still unclear which functionality the dock will have with these lenses. Only firmware update or AF adjustment as well?