Correct me if I am wrong, but the last time I looked at the A.net discussion it was all speculation. I would not put much weight on it.
Now, for my speculations, NW has only recently purchased its last (or alsmost last) 757. No rush to replace them yet. New A333 and A332 coming online as we discuss this. Not a great time to trade in planes. I would not look at NW for the 7E7.