Canon is in a dilemma here. Of course they'll discontinue the 5d2 (the name 5d3 alone states that), they just kept it around because they raised the 5d3 price tag so high to make money from early adopters.
But the pricing of the 6d will show how Canon expects the 5d3 to develop, because the gap cannot be too large if the 6d hasn't got any distinct features like built-in flash or flip out screen.
and... keeping 5D3 price high allows 5D2 to look like a bargain in comparison so it will sell out inventory without having to discount it.
Once it's gone the 6D may fill that slot so maybe not real down pressure on 5D3 price.
D600, however, complicates buyers' options if they're not too tied to Canon glass but even then you can sell it and get most equivalents from Nikon.