I have the 16-35 II. It's my favorite lens and it's amazin, dunno what the fuss in this thread is about? Why would you waste effort on a jerry-rigged manual 14-24 experiment (that makes absolutely zero sense).
Nikon's 14-24 is un-officially a replacement for it's 14mm prime lens, and is known to be a superior lens than it's prime 14mm. Canon's 14mm lens is known to be a better lens than both Nikon's 14mm Prime and it's 14-24mm zoom. 16-35 and 17-40 are much better focal ranges for photo-journalism style shooting.
If you aren't worried about a photo-journalism useful focal range, before you do something goofy and at an extreme waste of money, get one of the Tilt-shifts or the 14mm prime and pair it with your favourite zoom to compliment it. 16-35 II and the 17-40 are amazing lenses and awards have been won with these things. another tip, the 16-35 mark I (discontinued) is also amazing and well worth considering and can hold it's own up against the other two. Look at photographs taken with these lenses in the right hands, they are all over the net, and if you can't make pictures like that, then I can assure you Canon coming out with a new lens isn't going to help you out at all.
Here's one place you can check out samples (many pages to look through 16-35II at the time of this posting is on page 3 of the threads list / I also recommend starting from the back of any lens thread to see the newest images first) http://photography-on-the.net/forum/forumdisplay.php?f=107&order=desc
This dude has a ton of photos taken with 17-40 on crop body and 16-35 on full frame: http://www.dogfen.com/index1.html
He was awarded National Geographic's World in Focus grand prize in 2009 with the 17-40 http://www.creative-journeys.com/?p=2390
(that's for his article, there is a much higher quality version of that picture on his website under the Guizhou section and it's utterly stunning)
hope that helps you guys/girls