The only carriers I can see supporting an A380 to Seattle are BA/LH/EK.
SQ and QR have no A380 destinations in the Americas, it's all 77L/77W and A350.
Etihad doesn't even fly to SFO, and LAX is 4 weekly. No way EY flies to SEA before restarting SFO.
KE's A380s are way too premium-heavy for a small leisure-heavy market like SEA. They struggle to get 80% load from SEA (and SFO) with the 77W, and there are only 10 A380s in the fleet, they're more suited to JFK/LHR/LAX.
Asiana is similarly out of the question, they only have four A380s, and already get high load factors with the 77L/359.
BA/LH *might* work due to the booming cruise ship industry in Seattle, and connecting tech traffic to India (where LH competes with EK). It's still a tough sell considering LH flies the 333 into SEA during winter, and EK prefers the additional belly cargo of the 77W (to shuttle aircraft parts from Boeing Everett to their maintenance base at DXB).
All of this is moot though, since the Port of Seattle will never shell out the money for A380 gates.
By the way MUC-SEA, MUC-BLR and AMS-BLR (which can feed into Delta's SEA-AMS flights) were all recently announced