If I was Delta, and I wanted:

1. to go anywhere in Asia, nonstop, from the US,
2. same as 1 except include really far away southern reaches of Asia, nonstop, from the US,
3. and I knew the RASM-CASM margin using a 747 wouldn't be just right,
4. and I knew the RASM-CASM margin on a 777 wouldn't be just right,
5. and I knew the capabilities and margin of the A350 or 787 were just right,
6. and I knew the A350 availability was just right but 787 just wrong,
7. and I knew I wanted to be going from the west coast,
8. and I knew SFO was full of competition,
9. and I knew LAX was packed out,
10. and I knew SEA was open with no much international competition,

Then I'd probably order A350s and massively expand international flying out of SEA.

I'd need feed. If Alaska wanted to do it, then hire Alaska. If unable, or contract issues would prevent it over the long run, then fine, hire Delta.

If you asked me, what about Alaskan Airlines? I'd say as the owner of Delta, what does that have to do with my international flying to Asia? If those two things have issues or could complement each other, I'll do some what about Alaskan.

So I agree with the sentiment the two can coexist.

That's my guess.