That is my guess too. I imagine DL (and partners) will have preferential use of the A gates for international trips, though obviously given the fact that the Common Use “Club at SEA” is also remaining in A (underneath the new SkyClub), the airport’s vision is that at least some of the international flying from the A gates will be used by non-Delta (and non-Delta friends).
I also believe that outside the international peak hours ~noon-3ish, that DL will be allowed to use the international capable A gates for domestic flying.