I'm with others here and agree this lens is not something Canon are planning to release. (Not saying they won't have a 24-70 2.8 IS anytime, just that I think this one was probably a design that they tested and then decided against in it's current form.)
Personally, I would probably pay an extra $500 for an IS version over the 24-70 II - because $500 is only a fraction of what the total cost would be anyway. However I would never buy the 24-70 II at it's current price.
I'm looking to upgrade one of my 60D's to a used 5dmkII and I think I'll get an original 24-70 as my main lens for a few reasons - I shoot mostly video so version II's extra sharpness isn't needed for me - even for stills, the 24-70 will be sharp enough for my uses. The used price on the original will hopefully fall as people dump theirs to upgrade (if the new version ever arrives!) so the savings would be even greater compared to the version II. I also am kind of dissapointed that the new one does away with the reverse zoom mechanism - when combined with a lens hood, this feature was the next-best-thing to an internal zoom. In wet weather (which we've had a lot of here lately) the hood keeps the inner barrel dry, which prevents potential disasters!