Think the only way we are ever going to get one is on a dedicated route such as New Haven - Springfield
It gets brought up often, and I am a huge proponent for it. I've suggested multiple times Amtrak packs similar to the Cargo Line DLC's that would add services to the various routes that host such, as well as advocated for the Metro-North dual-modes to be added to Harlem despite their limited capacity. Maybe we'll see DLC for them for Stamford once that's out, or possibly a Hudson Line route if they ever decide to tackle that? Regardless, hope for the best, but don't hold your breath.