I spoke to the Canon US service center in Irvine yesterday, and was told:
a) the firmware itself is not yet available; keep watching the support site
b) the newest bodies (e.g. 1DX, 5D3, 4Ti) will be able to update the lens firmware
So if you have one of the affected lenses, but not one of the newest bodies, find a friend that does so you won't have to ship your lens to a service center.
Strange just got the new firmware installed on my lens.
Done in the Netherlands by Techrepair.
When checking the firmware you also see the 600 II firmware now.
The lens Firmware will not be available for download (like camera firmware) !!!