Is there any talk of expanding Amtrak Cascades to Sacramento? - Trains Magazine

As has been noted, most of southern Oregon's biggest towns are actually on the old Siskiyou Route (the original California - Oregon route, now largely paralleled by Interstate 5).  But that rail line is very problematic -- steep grades, tight curves, narrow tunnels, and poorly maintained by the current shortline owners.  Amtrak did, once long ago, run a Talgo demonstration train down that route, but nothing further ever came of it.

Caltrans has a general desire to extend daytime Amtrak California service north from Sacramento, through Chico to Redding (each with about 90,000 population, though Chico also has a large state university).  However, UP has said that they are not interested in hosting any more passenger service, and Caltrans hasn't pushed the issue.

Given the Coast Starlight's current overnight schedule between Sacramento and Portland, the beautiful Mt. Shasta scenery, and the Starlight's current popularity, there might be a market for a daytime train (in effect resurrecting Southern Pacific's Shasta Daylight).

Given UP's current attitude, and other budget priorities in Califonia and Oregon, any expansion between Eugene and Sacramento seems highly unlikely.