2014 Winter Olympics
We're told that the replacement to the EF 100-400 f/4.5-5.6L IS will be making its way into the hands of select photographers at the Sochi games in February, 2014. It was unknown if an announcement of the lens would happen beforehand or if it would be used as the final test bed for the replacement lens.
I'm not too sure how many people would put down their 200-400's for one of these, but the mobility factor may make it worthwhile in certain situations.
A grain of salt on this one, it's from a new source.