Too many people to quote, but appreciate the discussion SuperEWR and The Situation. As a Seattle resident, I hope you are both right.

That being said, and I'm happy to be wrong, I just don't see how DL can meaningfully step to getting enough connecting traffic to Asia out of SEA to sustain anything close to a competitive network to AS - right now Delta actually flies more to Europe than Asia (as others have said) ex-SEA, and their non-China routes are both covered by a non-ST airline. Where are they going to go? TPE is covered by EVA (and Starlux at some point), SIN by Singapore and then the ME3 as well as TK also have a successful presence already. With Alaska entering OW, they're going to be able to build a motion to get those same passengers connecting through SEA, with a better domestic network to go along with it.

Looking at the broader network, it sure seems like DL is planning to send as many people through ICN as the primary Asian gateway - why would they overfly ICN for BKK when UA can't even make that work from SFO?

Ultimately DL might think they can bide their time and keep growing corporate accounts and local traffic while building up a trans-pacific network, but if their strategy is going to take 10 or 20 years to roll, that's a long payback period - especially if the economy slows down at some point in the next couple of decades. SEA makes a great gateway to Asia, but that's the only thing it's well-placed for - SLC will seemingly always be the hub for moving people through the West, can SEA handle playing second place with just local demand and whatever they can wring out of the rest?