gokeefe wrote:Given what's being done with the diners I'm having a hard time imagining a major service expansion
I'd say quite the opposite. What's happening with diners (being downgraded to cafes) makes it easier to add sleepers.
Fundamentally, the trains where a dining car can perform well are trains with lots of passengers on 5+ hour trips going through a meal seating (e.g. boarded before 6am and getting off after 11am, boarded before 10am and getting off after 3pm, boarded before 5pm and getting off after 10pm). For a passenger like that, the alternative of getting a meal before boarding or after deboarding isn't viable, so it's a question of dining car vs. cafe vs. packing your own from home.
By the same token, the trains where sleeping cars can perform well are trains with lots of demand for overnight travel.
For the Chicago <-> West Coast trains (and arguably the Sunset east of San Antonio), there's enough of both factors to allow the diner-sleeper link to work, but otherwise, the exceptions are pretty rare and mainly based on running long enough with enough endpoint-endpoint demand (maybe the Coast Starlight?), or having so much demand that you can effectively segment the service (which is arguably what was observed with the Silver Meteor and Silver Star, where the Meteor being a more premium offering for NEC <-> South Florida).