I have no interest in this lens. Who else has no interest in this lens? Is it just me? F/5.6 is only useful when you're already compromising because it's a zoom. I've tried the current 400 f/5.6. It's a fine lens for what it is, and considering its age.
But I have no interest in an approx. $2000 fixed focal length 400mm f/5.6 lens. If it were f/5, maybe...but not f/5.6. If it were no more than $1450 at introduction? Perhaps, but I doubt it will be.
Before I spent $2000 on a lens like this, I would rather use other less costly lenses and save up to buy a used or refurb 400mm f/4L DO. It's entirely possible prices for those will dip into the low $4000's at some point, especially if a new f/4 model is never announced. If Canon ever get around to bringing out a new 400mm f/4 (whether DO or not), it will cost $9000, thus prices on used 400 DO's will go up, rather than down.
Just my opinion and my thought process, no doubt others will differ.