I hope Canon realises that the top end of the 400mm market is already well catered for. If they choose to discontinue the 400/5.6 then a new 100-400 really needs to be similarly priced to the current model. Otherwise, they'll price themselves out of the market and will slowly start to lose their reputation as the "go to" brand for enthusiast sports and wildlife photographers. There is precendence for new "affordable" 400mm lenses. The Sony 70-400 comes to mind.
That were my thoughts in the beginning of the the year and I decided to buy a 5.6/400 lens due to its great IQ, fast AF, sturdy design and ... built in lens hood. I found ONE online camera seller who offered that lens regularly and paid 1240 EURO. Now it costs 1600 EUR by the same camera seller!
Something might be going on ($ to Euro exchange rates explain 10 or 12% but not 35% price increase) and if the 100-400 is replaced by a 3000$ Mark II successor the 5.6/400 will sell for a lot more money because it is the cheaper option. Until it will be replaced by an IS version for 2500 $.
Some of you have discussed about 100-400 vs. 400 and used the argument that you use a 100-400 most of the time at 400mm - I think that's correct. But for me just a 400mm lens might be a walk around lens. Her in germany the landscape is cluttered with disturbing artifacts like power lines, storage depots, drive ways, etc. - a 400mm helps to cut out photographically interesting compositions. But several times I have missed the flexibility to change the focal length to 100mm if the landscape wasn't spoiled. (Just for those who are in the process of decision making.)
A last remark: That's the point where the EOS M system might come into play. The EOS M with EF adaptor and the EF-S 60mm is very light and compact ... and a good complementation to a 5.6/400 ...