This lens might be Canon's response to the Nikon 200-400mm f/4 VR, and the early announcement might be an attempt to keep people from jumping brand. This would mean this lens' price would be similar to that of the Nikon (read: ~$6,500), possibly with a premium for the built-in 1.4x extender.
That would mean this lens doesn't replace the EF 100-400mm f/4.5-5.6 (which, I assume, competes with Nikon AF VR Zoom-Nikkor 80-400mm f/4.5-5.6D ED).
The photo has a metal loop that I think is not a part of the lens, but rather a part of an anti-theft device (the one with a metal wire that has a lock on one side, and a big lump on the other side that wouldn't pass through the loop).
If I'm right, that might mean that the lens isn't just being display (as in, maybe this is just a mockup in a glass box), but a prototype that people can play with in CP+ (Feb 9th-Feb 12th, - in a couple of days), which means production could be significantly closer than Dec 31st.
