Okay, here's my two cents. I had a very knowledgable FA on my SEA-HKG flight earlier this week (I know, most FA's seem to be misinformed, but this guy was spot on discussing the AS battle and the code-sharing problems with KE, etc.). He seemed to think SEA-HND was here to stay, especially as NRT loses focus and HND seems a better option for O&D to TYO.
He also mentioned SEA-TPE starting sometime next year, which I guess has been talked about for some time, but it is nice to know the Seattle hubbing will continue. I don't see how discontinuing the HND service out of SEA makes sense in that grand scheme, even if they're having trouble selling seats at the moment.
When I looked at fares for SEA-TYO this winter, I did see that some of the cheaper fares had connections at LAX. I would have thought DL would drive traffic the other way, having California customers connect at SEA, but perhaps LAX is also gaining or maintaining its size even as SEA hubs.