I think we've workshopped that one pretty thoroughly in other areas and come up with little. I don't know enough to back this up, but perhaps the Talgo is an idea who's time has come and gone but national pride in Spain keeps it under construction. I'd be curious to see annual production numbers. Aside from Spain and Portugal, there are something like ten trains in the USA (half built in Wisconsin), five in Argentina, two in Uzbekistan, three in Kazakhstan, etc... Not exactly a well-embraced technology.
Would the next generation of Cascades be better served by a Siemens product that looks like Brightline? Or perhaps by secondhand Caltrain MP36 and BBD cigar cars rebuilt for long distance seating purchased after electrification? The Starlight has an hour additional in the timetable to Portland, but how much of that is equipment (tilt) limitations and how much of it is just not pushing a slow long train because BNSF doesn't want to? How much curvature was eliminated by ditching the waterfront line south of Tacoma? If the answer is the latter two, perhaps a deep dive is necessary.
This leads to another important point in long-term equipment planning. Buying rare and one-off stuff like Talgo and Acela means there is little chance of selling them or reusing them. If we had bought an ICE or X2000 instead of the Acela, perhaps the Argentines or Kazakhs would buy it for their perpetually under development HSR. Perhaps they could be used in Keystone service or towed by a diesel. But its clear nobody wants standard gauge Talgos, even brand new, and nobody wants the used Acelas. That hobbles future developments of corridors.
The new Acela: It's not Aveliable.