Big Green, I would think that there is a market for service to/from Bellingham and Seattle. According to the
Amtrak Cascades 2010 Performance Report - February 2011 (pdf 471 kb), Bellingham ranks 6th in passengers among the Cascades stations.
Amtrak offers four Thruway buses each way north of Seattle, but only one of the four actually serves Bellingham. (I've heard that that's because of limitations of where Canadian buses are licensed to stop.) So Amtrak and WSDOT could create a third train frequency, which would improve options from Bellingham. Southbound, I would think there'd be a market for a 7 AM departure that would connect to the CS, or a 2:30 PM departure that would connect to Cascades 509 to PDX and EUG. Move it back an hour and it would connect with the EB.
Northbound is a bit trickier. Do we replace the 12:20 PM bus that connects from 500 and the EB, the 4:45 PM that connects from 506, the 9:15 PM that connects from the CS (and which might have to hold if the CS is late), or do we create something else?
Of course, while we're dreaming, let's take a couple of the Talgos being freed up by the ones Oregon is buying, plus a couple of (ahem) surplus ones from Wisconsin, and create a daytime version of the Empire Builder over Stevens Pass, or a new train over Stampede Pass. Some folks in the rail office at WSDOT talk seriously about such options, but there's no money unless they get a windfall from Bill Gates