If Delta adds London and Hong Kong as rumored. I can see Alaska removing the Cathay codeshare from Seattle and I can see Alaska ending its relationship with British Airways and adding Virgin Atlantic. The removal of the Cathay codeshare (not the marketing relationship) would cost Alaska a fair amount of money. Not sure a Delta's SEA-HKG flight replaces that lost money. So you have to imagine Alaska and Delta would have an "arrangement" that works for both airlines. But BA for VS (IMO) makes no difference financially to Alaska and would be a "good will" gesture to Delta.

And with that, my last prediction....Alaska has a codeshare/marketing relationship with US Airways by end of year assuming AA/US gets merger approval.

Alaska will maintain both American and Delta codeshares/marketing relationships.