For what it's worth, I got notified Saturday that I'd been downgraded to Coach for an early October CHI-RNO one-way trip on the California Zephyr. Called immediately and was able to salvage a roomette (had been in a family bedroom) the entire way, but have to switch rooms and cars in Grand Junction. Based on dummy bookings today, all sleeper space is now sold out from Denver to Grand Junction.
Anyone with sleeper space on the western long-haul routes this fall should keep tabs on their reservation and be prepared to call immediately of things look out of sorts or they get the dreaded email or phone call. You may have to consider switching rooms en route or even hopping between Coach and First Class one or more times. If you have to switch, keep in mind what time it will be then (both scheduled and if it's running late) so you aren't doing it in the middle of the night. Good luck.