The company put out a communication recently to all of the employees confirming both of these rumors.
Alaska has been working with the port in L.A. for a long time trying to find a better place to relocate to that makes better sense given the number of international flights they operate there. Terminal 6 is a natural, given the close proximity to both AA and DL/NW.
SEA facilities are changing as well. Alaska will be giving back the majority of D gates and taking over all of the N concourse. That would leave Alaska on the C concourse and the N concourse, with a minor presence in the D concourse I believe. I imagine, though I haven't see it in writing anywhere, that they would want to put a Boardroom on the N concourse. The Red Carpet Club is nice but it is definetely a dark space - I wonder if they would use that same space?