I really think Nikon has nailed the potential of diffractive optics with their new lens and hope that Canon will follow suit.
So...you hope that Canon decides to release a DO lens where they have to warn in advance about flare problems, claim those problems can be minimized by a post-processing software correction, and provide an example of that correction where the resulting shot still suffers badly from veiling glare? To each their own, I guess...
I meant with the DO tech of the 400mm DO II which evidently suffers none of the above.
My point (which I suspect you got) is that $2,000 is accessible to a lot more users than Canon's $7,000 asking price. The 400mm DO II is out of my range whereas a 300mm f/4 DO at $2,000 would be attainable for a lot more of us. Needless to say, we're talking about Canon so we can be fairly sure that isn't going to happen.
Canon's optical solution appears to be far more effective than Nikon's half baked optical and software solution, so no wonder they're selling it for only $2k. I'm sure if they figured out a full optical solution the asking price would be in the same region or more than as Canon, as they do with their 70-200. By the same token, if Canon do offer a 300 f4 DO it will be an optical solution and priced accordingly.