There is another possible source for some -400s. I mention this not to feed rumors, but because it would make sense. The new CEO just dealt with the Atlas pilots major issue (STN). If he wants labor peace it makes sense for him to deal with the Polar's pilot's major issue.
As long as Atlas does not get stripped of airplanes (I am an Atlas guy) and this rumor is true, I think this is a good thing. We need to get this merger done and behind us, and the more working airplanes in the final mix the better for all of us.