I think DL and AS will coexist. But, DL seems to be going after AS by adding routes like RDM and AUS in the latest expansion. I don't see DL wanting to commit the number of planes needed to compete on every AS route out of DL.

I think for people who fly a lot, those who travel along the west coast and major eastern and Midwest cities that have nonstop service on AS out of SEA would go with them. For those who fly internationally and to smaller eastern and Midwest cities that require a connection, they will choose DL. Despite all of AS's international partners, it's not quite the same as having an elite status with one of the three alliances that includes more perks including lounge access.

I do think it was AS who pulled the plug on this "partnership" based on the timing which was happened pretty quickly after the merger closed. DL still has use for more feed in SEA.