[/quote]I am in the same boat. There's no real IQ improvement in the 16-35 f/4L IS. They are the same at equivalent apertures. The fact that they are the same weight and size, and that the 16-35 f/2.8L II goes to 2.8 convinced me to skip the f/4, but an 11/12/14 - 24 is more tempting. I realllly hope they go with f/4 on this to keep the weight down, because f/2.8 is bound to be big and heavy, not to mention much more expensive.
I agree about the IQ between the f4 and 2.8II - contrast looks marginally better at f4 w the former, but not really worth replacing a lens over and at f8 where I shoot landscape from a tripod, its definitely not worth a switch (pending further data).
11-24 w or w/o f 2.8 is intriguing. I'd go with the best IQ formula and only prefer 2.8 if it did not degrade the IQ at f4 and above. Size, weight + cost less important for the applications I envisage.