There is no way Amtrak will do this, as it would double T&E crew costs, since each separate train would require its own crews. It would also increase the number of locomotives required, with associated fuel and maintenance costs.
When the Diner/Lounges were first introduced, there was some serious discussion about running a Diner/Lounge Portand-Spokane and running the Sightseer to Seattle. That would have provided lounge service to Seattle and diner service to Portland at much lower cost than a separate train. It was one of the few logical uses for those cars, for which Amtrak mutilated perfectly good dining cars to create.
They probably would not even consider running separate sections unless the combined consist exceeded a13 car max. The maximum consist in my recollection was
Seattle section (7/8)
Baggage
Transdorm
Sleeper
Sleeper
Diner
Coach
Coach
Portland section(27/28)
Sightseer
Coach
Coach/Bag
Sleeper
Sleeper
CHI-MSP cutoff (807/808)
Coach
Since they are nowhere close to running that max consist, largely due to ongoing post-COVID equipment and staffing shortages, an entirely separate train is pretty far off. In any case, since Amtrak management is focused almost entirely on cost containment and ignores revenue enhancement, if they ever again reach max consist and still had further demand they would happily accept the increased sales in higher price buckets while avoiding the the direct costs associated with more service to meet that demand. This despite that increased service makes for better utilization and more revenue to cover fixed costs.