It was reported to be heavier than the 400/2.8 IS II (3850g).
If so, that would turn this white elephant into an even worse fiasco than the 400 f/4 DO.
The problem with the f/4 DO is that, sure, okay, it's comparatively small and lightweight. But it's still big and heavy, it's still very expensive, it's slow, and it doesn't have great image quality. Indeed, except for weight, the 300 f/2.8 with a teleconverter is comparably priced, much better optically, and much more versatile.
If the 200-400 is as expensive and heavy as the rumors are generally agreeing upon...well, then, you've got a lens that's heavier than the 400 f/2.8, slower than the 400 f/2.8, and roughly as expensive as a 400 f/2.8. That's an awful lot to give up just for the convenience of flipping a switch for the teleconverter.
The lens isn't going to have significantly better image quality than the other Great Whites; they're already close enough to perfection that, though there's always room for improvement, there's never going to be room for much improvement. So if it's not going to be a clear winner in terms of IQ, if it's not going to win on price, if it's not going to win on weight, and if it's going to lose pretty significantly in terms of speed and reach, if all it really wins is the convenience factor at the cost of all those other disadvantages...well, it's going to fit a very small niche indeed.
When it comes right down to it, it really seems to be nothing more than a grossly overpriced and overweight upgrade to the 100-400. I'm still thinking the classic combination of a 70-200 f/2.8, a 400 f/2.8, and maybe a teleconverter is going to mop the floor with this new lens for all but a few edge cases. (And, yes -- I know those edge cases exist, and those who spend a lot of time shooting in said edge cases are going to buy this lens no matter what.)
I'd really love to see a lens like this succeed, but either the weight or the price would have to be dramatically improved for me to have much hopes for it. Put the price at (or below) $7,000 and leave the weight or keep the price where it's rumored and get the weight under 7 pounds. Not much else, I fear, can save it at this point.
Regardless, that Canon actually officially announced this before the first copies had come off the production line is unprofessional. Go ahead and announce it before you've got enough on hand to sell, but don't announce it before you've actually got something in your hands you happily plan on selling. It's that whole thing about counting unhatched chicks....
It's a shame, too. Canon is the undisputed master of the supertelephoto. If anybody was going to pull this off, you would have bet on Canon to be the one to do it. That they're flailing around so miserably suggests to me that some heads should already be rolling.