What a ridiculous idea
It seems the reason for this is a weak attempt at slowing down massive attrition. Combined ERJ/CRJ losses were almost 1,000 pilots for 2015. United knows that may become a problem at some point.
So this may keep senior guys around a little longer to see how their interview goes. And if it is mapped out along the same lines of the Commutair deal, it may bring more new hires our way.
But for anyone below maybe 500 on the list, the mid level CA/FOs... there is no way this makes anyone at that level (most of the list) stick around to wait and see what they get. Only way to achieve real staffing retention would be to interview everyone immediately, and tell you whether you're going or not as soon as possible.