I am a FO with Delta, so my chances for upgrades are extremely small by default. So, I decided to use some hints I learned here and from ThePointsGuy. I had two situations:
1) PDX-SLC. I was #5 on upgrade list, 1 seat was unclaimed (according to delta.com, since there are no monitors at PDX). When all passengers boarded, I've asked GA if first class boarded in full, and was told that "yes, everybody on board". I was the last person who boarded, behind me was only a GA. To my surprise, I saw one empty seat and also saw that GA gave a new boarding pass to one passenger who was sitting in the coach. So, that person got this last seat. I wasn't upset since it was a short flight.
2) SLC-JFK. I was #6 on upgrade list, 1 unclaimed seat. People started boarding, I decided to wait and happily watched how my position changes in the upgrade list. When only name was listed on the upgrade list and monitor was showing that 1 seat is still unclaimed, I approached to GA. I told him that I am #1 on the upgrade list and I see that 1 seat is still unclaimed. He told me that my position is #6 and 2 diamonds are boarded and he is going to give this seat to one of them. I politely told him that if I am not mistaken, if the passengers boarded he looses his position on upgrade list (what was exactly shown on the monitor). But GA laughed and told me "No,dude, it cannot be". We laughed about it, since I understand that for Delta Diamond is obviously a most profitable passenger than a FO.
So, since you guys know better, is it a new Delta policy to upgrade the next person on original upgrade list and not the person who waited until the last moment?
Go play the Lotto. You found 2 needles in one haystack!!!
While I prefer this method, it is not the "rule" as followed here on FT. Could we hope this is a change? I would, but I doubt it.