That's also a list I'd like to see from Amtrak, but since we haven't really discussed it here I'd be happy to entertain. My response would be whichever routes couldn't be replaced entirely with corridors services along chunks of the route, even if they are seeing high end-ish to end-ish ridership. The only 2 that I could most likely see frequent corridor services covering all or almost all of the route would be:
Lake Shore Limited - NYP-Toronto, Chicago-Cleveland. If NYP-Cleveland via CNY were also viable for corridor service then you have the entire thing covered
Crescent - NEC, WAS-CLT, CLT-ATL. Jury is still out on NOL-ATL, but that could easily be filled in with a truncated Crescent
Some others I could see being truncated to just cover the portion of their route that wouldn't justify corridor service:
Coast Starlight - Seattle-Bay Area
Texas Eagle - Chicago-Dallas
Silver Services - South of DC only
Builder - MSP west only
Cardinal - CIN-WAS
Crescent - ATL-NOL
I'm not saying I agree entirely with these, just that if something had to be cut, it should be only where alternatives are created. Unfortunately though, since the portion being cut is likely the main generator of ridership from that end of the line, forcing a transfer for many of these services could potentially kill the ridership. But "bridge trains" or truncated LDs are better than no service at all. Also, some of the LDs run along the potential/existing corridor sections in slots that would still be useful on both sides. The Carolinian is a perfect example of that in both directions (might actually be the only one though). Is travel between NEC stations permitted on the Carolinian? If no, how frequently does the train go out with spare capacity? If the number is consistent enough perhaps Amtrak could sell whatever that avg percentage is for NEC travel and cap it at that.
Re-tooling some LDs to provide overnight service between major corridors could also be an option. They still serve the smaller communities and become even more useful for travel between major regions (rather than losing a day en-transit you're saving $$$ on accomodations).
Long and short though, nothing's gonna change. We'll get a couple of nominal enhancements and then politics will sadly force the person arguing for rail where it actually makes sense out the door.