6) This new lens will replace the 24-105, eliminating the 70-105 overlap that current lens has. This is a deliberate move by Canon to sell more 70-200 glass. (I have poked a few holes in this theory, but it's as plausible as anything else on this list).
Eliminating the 24-105 would certainly be a consumer hostile move. The focal length overlap certainly did not stop me from getting a 70-200. The overlap is extremely useful in my work. There are some jobs I do pretty much entirely with the 24-105, whereas if I had the 24-70 (one of the least interesting focal ranges I can imagine - my opinion only), I'd do a lot of switching between the two lenses.
Someone earlier called the 24-105 "slow." Could not disagree more. I use it all the time for basketball in gyms with permanently mounted studio flashes or with my own flashes temporarily mounted. On the 7D, I have ideal reach all the way from right under the goal to three-point land. The f/4.0 max aperture does make manual focus difficult or near impossible, but fortunately, I get a near 100% AF hit rate.
I'd look at this rumored 24-70 as a secondary lens, possibly for remote mounted use or when more compactness is desired, such as for recreational shooting, especially if it addresses the 24-105's minor optical shortcomings (distortion/curvature at edges).