I was invited to a Canon/Cathay Photo Preview Session in Singapore in January this year (2013) purely about the 200-400f/4 (1.4x), We were able to play with production Lenses (According to the Canon People there these were Production Lenses), we could use our own cameras, but no Cards, on both my 1Dx & 5DMK3 Bodies this lens feels & looks the part, until we get to view Images we wont know for sure, but I feel it's at least as sharp as my 400f/2.8 V2 Lens, time will tell. Weight wise a fraction less than the 400f/2.8, maybe a few mm's shorter, it's not a small Lens, hand holdable if your reasonably adapt at holding the 400 V2.
Pre orders were taken at the Viewing by Cathay Photo, and an "estimated" delivery time was given of "Before June 2013", Since then I've heard nothing to detract from that statement, other than I have read a report that the Lens has been delayed due to "redesign requirements" apparently (I cant confirm this is real), there were reports after the London Olympics that the Flip switch for the 1.4x Converter was poorly placed in relation to the 1Dx Body/Controls on the Camera.
So, who knows, Canon are mind blowingly Obtuse on the matter, this Lens as we know has become the "Mythical Monster", I sincerely hope it will be this year, I have a Tanzania "Migration" shoot coming up in june/July for 4 weeks, I had hoped to have this Lens, I plan now on taking the 300/400 & 600 as I have no confidence Canon will have this Lens available by Mid this year, end of this year ?? Probably, I mean, Nikon have had a reasonable one for 10 Years.