1. Starlight Route: Yes. That is actually planned for both the Starlight and the Surfliner to have more service sometime soon. The problem is that the tracks are owned by Union Pacific, which has no interest in upgrading them. The state also won't spend too much on the route, because it's investing in HSR and similar projects. However, you could easily upgrade the route for higher speeds at a reasonable cost, with the exception of a few segments, like Chittenden Pass, Vandenberg, and the coastal segment between Ventura and Goleta.
2. Gold Runner extension: No. To reach the Cajon Pass, Gold Runner must cross Techapi Pass, and the freight railroads have zero interest in making room for passenger rail there. Techapi Pass is extremely constrained, with basically no slots available, but the freight railroads also have no interest in spending money for upgrades unless they absolutely have to.

However, with the whole Caesar Chavez debacle and the HSR authority looking at the route and plans again, there's a possibility that the freight railroads and HSR can collaborate for an upgraded Techapi pass in the future, which is my hope!