My thoughts exactly:
I bought my 5D3 and 24-105 f4L IS kit back in April and I have to say that I've been very happy with the results that the 24-105 produces.
Things such as cost and IQ being approximately equal, would I...
Buy a 24-70 f4L IS to complement my 24-105 f4L IS? No - I'd rather go for a f1.4L wide angle prime to complement the zoom.
Trade in my 24-105 f4L IS against a 24-70 f4L IS? No - I can't see that I'd gain much by doing that.
Trade in my 24-105 f4L IS against a 24-70 f2.8L II? Well, I do regard that as an upgrade and it's not out of the question one day, but...
Trade in my 24-105 f4L IS against a 24-70 f2.8L II IS? Absolutely!!
The point I'm trying to make is that if Canon intends to replace or supplement the 24-105 f4L IS (kit) lens with a new 24-70 f4L IS (kit) lens, that in itself won't make a lot of difference to me and, I suspect, probably not to many others who already own the 24-105. I'm happy to wait a year or so to see what happens with the 24-70 f2.8L II. Either there will be an IS version as many here hope, or the price of the f2.8L II will drop to a more affordable level.