There are many original national system trains that have disappeared too (National Limited, Broadway limited, Lone Star/Texas Chief etc.), as have many "what Amtrak giveth it taketh away" trains (Desert Wind, Pioneer). So the point is, something having been a National System train does not carry much weight in this sort of an argument, unfortunately.
Can Amtrak actually withdraw service unilaterally, or does it have to go through some formal abandonment process.
I guess indefinite temporary suspension is a loophole to effectively abandon the service without having to jump through all the hoops.
Amtrak has to give a 6 month notice in any discontinuance. But then, if they plan to ever restart service, they then have to renegotiate a contact with the railroad(s) involved. (And probably have to pay for upgrades, signals, ect... - but if they "temporarily suspend service (like they did for the past 6 years), they do not have to do so. They can go by the old contract.
So they do not want to "discontinue the route"!