Given what Delta went through to score their new batch of HND slots - and how twitchy the US DOT got about them failing to operate it consistently the last time they ran SEA-HND - I think this is one of the last routes they would consider dialing back capacity on. While most of Delta's network will probably be adjusted for capacity or frequency, I think Haneda will see fare sales instead in an attempt to stimulate demand.

That said, I'm not currently seeing fares out of the ordinary - $950 in Y or $1400 in PE is pretty standard advance purchase pricing out of SEA.