As much as there are gains for Nevada and little actual perceived value for California with a Las Vegas HSR route, the overall networking value of having a point in which two systems can actually connect as seamlessly as possible makes the whole system that much more valuable in the long-run. Much like the former Class-1's had with their individual routes connecting in many cities, and in a different manner the many Amtrak routes interlacing and creating a network for passengers to get from one city to another even at the cost of making a connection, this too could be the beginning for something larger.
So, lets just say that the CAHSR project goes fully as planned and the mainline route establishes a hub of sorts in Palmdale. And then lets say a HSR route to Las Vegas also gets built. Once up and running, with actual passenger numbers and revenues flowing instead of hypothetical projections, these two true Bullet Train routes set a standard in the USA that is no longer just a pipe dream but reality. Would it stop there? Remember that CAHSR is not just to LA, but San Francisco, San Jose, Sacramento, and San Diego with all major cities in-between.
Could, say, a route between Las Vegas and Phoenix be drawn up next? Because I'll bet thats a pretty large market for the casinos in Vegas too.
What about Denver to Vegas?
Denver to Chicago?
The limit is your imagination at that point.
For a HSR connection with California and everything east of the Sierra, going via Vegas would probably be the most realistic. Just my $0.02.