I'm pretty sure BOB2 (the real one) has discussed night trains in California several times. Likewise adding frequencies on the whole Coast route, not just the north and south ends. Main issue, as always, is money - to start up and to run. The state would have to pay for it, like it does the Cap Corridor (extension to Salinas is on the books though not scheduled already), surfliner, and San Joaquins. The state (HSR notwithstanding) is not in the business of funding poorly-used trains, though, and the night trains in general, that have been tried (remember the MedFly?), have not been heavily used. In a time when there are hourly or better flights between most of the major northern & southern CA airports, taking an hour, for much of the day and evening, there's only a limited market for "night trains." Would be interesting (and so far not easy to tease out of published data) to see what the ridership is on the "night buses" run by Cal Amtrak connecting the last San Joaquin with LA & SD, and connecting Cap Corridor and Surfliner.