I think this is an obvious replacement of the relatively old 28-135mm f/3.5-5.6 IS USM to go along with the 6D. I think it will definitely be smaller and lighter than the aforementioned lens (as well as the 24-105mm f/4L IS USM), and priced around $600 to compete with the Nikon 24-85mm f/3.5-4.5 VR. It would be the perfect kit lens for a first-FF DSLR buyer. It would definitely have better IQ and IS than the 1998.
Think about a 6D buyer looking at the currently lineup of FF standard zooms:
28-135mm $450 alone (big, heavy, old, fair IQ)
24-105mm $970 alone $800 kit (big, heavy, very good IQ, somewhat expensive)
24-70mm II $2300 alone (big, heavy, superb IQ, more expensive than the body)
...and that is all your currently-available new (not used) Canon options
Replacing the 28-135 makes total sense with the first entry-level FF coming out in a couple months. If the only option is 6D+24-105mm ($2900), it is more expensive than a D600+24-85mm ($2600), then Canon WILL lose customers, period. A more affordable is needed, and the 28-135mm is not the solution. A red ring and L in the name will elate potential customers (much better branding than Nikon's ED and gold ring designations).
That's a good thought. I never really considered it as a possible kit lens for the 6D, but that's the only way I see this lens making any real sense.
Again, if it's around the size of the old 24-85mm lens (or 28-105) and priced reasonably, we might have a winner, actually. A compact, lightweight EF zoom lens is missing from Canon's current line-up and this might be it. (then again, why not an update to one of those older lenses? More reach would be nice, for sure)
While they're at it, they should also consider putting out a smaller, lighter, non-L version of the 28-300mm lens. The L version (Canon's only FF super-zoom) is WAY too big, heavy and expensive for use as a walkaround...