I think they will drop the price to 800-1000 if you buy it with the 6d, I think it will be a $3,000 kit. They are giving the $1,499 price for the lens alone to promote the 6d, because amateurs either want a 6d or a 24-70. So, they promote a "steal" getting people to buy the 6d and the 24-70 f4 is together, the 24-105 will remain the walk around king, but they want to give ameutures a 24-70 option, so it is a true junior kit.
6d + 17-40 (or whatever replaces it, maybe a 12-24 f4?) + 24-70 f4 is + 70-200 f4 is (mark ii)
Canon is just trying to market both product with a kit. People who want a entry level ff want a 5d ii, and those who want a 24-70, want a 24-70 2.8 1. So canon wants to kill two birds with one stone, by getting people to buy the 6d, and a 24-70 f4 is which is as sharp as the 2.8 ii.
They want to sell the 6d and 24-70 f4 for the equivalent of a 5d mark ii and a 24-70 2.8 1 for the same price, and trick people into thinking its a steal, because if you want to buy one, you might as well buy the other.