Originally Posted by rylan

If the certs were not 'used yet (ie your were still waitlisted, or cleared but ticket not reissued to use the certs yet) then that shouldn't present any issue... the certificates are open and can just be moved to the new ticket.
The issue comes in if they are closed due to your upgrade being confirmed and ticket reissued and then you need to change the flight. DL is generally pretty good with the certs and getting them over to new tickets, but it is a risk if something gets screwed up.