I still don't get the point of the 24-70 f4 lens. It's more expensive than the 24-105, has less focal length range, and is comparable in optical quality. Why? Just why? If you want noticeably better optical quality, then go for the 24-70 f2.8. Otherwise, you're better off with the 24-105 for less money.
If you're right and Canon is going to discontinue the 24-105, then will they bring something to replace it or do they want to force users to a smaller focal length range so that users spend even more money to add a 70-200 version to make up for it?
And I also think you hit the nail on the head. The 24-105 is a fine lens to carry around that covers a nice range for many activities and casual snapping. I added one over a year ago and find it often on my camera unless I know I have a particular need. Typically the focal lengths I tend to shot at are the 35-42mm, and 85-95mm ranges. (with it open to 24 a good amount of time also)
It is very convenient to not carry 2 or 3 lenses even though it seems I would be happy with the 35 and 100mm primes most of the time. I've rented the 24-70 f/2.8 II to try it out, lovely lens. I just found myself wanting a little more at the long end fairly often, and the $$... geesh.
Faced with the discontinuance of the lens, I might opt for a non-canon 24-70, and think about the 100 macro also. ( I already own the 70-200 f/4, and don't want the weight of the f/2.8 )