Remember the 2010 stimulus package? Way back then, money was set aside to build new trains for Amtrak California. They were supposed to be similar to the existing bi-level models, but with an updated design, and arrive around 2016. Their arrival would allow for Amtrak California to expand train service on all three routes.
Unfortunately, the company who won the bid (Nippon-Sharyo), completely failed at that task. After several years of building a prototype, they said they could not build what they said they would. In 2016, Amtrak California announced a plan B: they would buy existing Talgo trains that had been built for Wisconsin, but never used. Except that never happened, and there’s no official reason as to why. They just stopped talking about it.