Also, for the Las Vegas link, the terminus is on the Metrolink line so you can take a commuter train from Union Station. People taking Amtrak from points east could get off at the Ontario station and it’s a relatively short taxi/bus ride to the RC terminal (Amtrak uses a different set of tracks coming into L.A. from the east than the Metrolink station serving RC). I suppose it would be feasible to extend the line a little further south to connect with Amtrak should there be demand (if they went to the Ontario station, then the Ontario airport could also be integrated into the service).
LA to SFO would be worthwhile but probably much harder.
Between Sacramento and Merced, and LA and Bakersfield, there will be a "high speed rail bus service". For other parts there will be regional commuter train and bus services.
Then, eventually, it'll become: https://hsr.ca.gov/wp-content/uploads/2021/03/Business_Plan_...
It’s like 2-3 hr drive between the two cities, and at both end you have to navigate auto transport, most likely a rental though maybe Uber would work out but at greater cost for anything beyond a single destination. I would imagine most people would just opt to drive, since they need a car at either end of that line?