Join Date: Oct 2005
Location: Ponte Vedra Beach, FL
Programs: DL PM, HH Diamond, Fairmont Prem, SPG Gold, Priority Club Plat/IC Amb, AmEx Plat
Posts: 10,839
At 3 hours before departure, all upgrades become battlefield. At the same time, 3 hours before departure, is when you can begin to SDC. So you won't receive an upgrade immediately if you SDC and will be placed on the upgrade list. Meaning, there is a chance you won't get the upgrade if others ranked above you SDC or purchase tickets that are upgrade eligible.
Your upgrade from the other flight does not transfer over. You'll SDC to your original class of service (and fare class).