Chris,
A quick look at the shipping schedule, and you'll see a TON of uncertainty/inconsistencies surrounding Lionel aluminum passenger cars and sets.
On first look, when Lionel catalog'd so many new sets in the 2013/2014 catalogs, I thought the Lionel aluminum passenger car issues were history. Then the Milwaukee Road 18" cars were finally delivered after an almost two year delay, only to find many folks here complained about problems with interior lighting/wiring. Turned out most of the issues centered around sloppy labor. And we haven't seen a Lionel aluminum passenger car delivery since. Lionel can't be happy with this situation. At least the paint scheme on those Milwaukee Road cars turned out exquisitely, and Lionel did a great job on the sky top observation.
As you noted, the Neil Young stuff has moved to May 2015 delivery ETA's, while other stuff catalog'd with it is still showing Nov 2014. But the N&W Pocahontas set that includes the #611J locomotive (reportedly produced well over a year ago with #612) has slipped more times than I can count -- now showing December 2014, and that was catalog'd well before the sets showing a Nov 2014 ETA. And the Lionel California Zephyr -- catalog'd as a 4-pack and two 2-packs -- is still showing a July 2014 delivery on the shipping schedule (after numerous slips) -- despite two shipping schedule revisions (7/30 and 8/27) that should have updated the delivery date for the CZ. Instead, it's still showing July 2014, which we know now hasn't happened -- nor did it ship in August either.
Logic would tell us that until we see sets like the CZ (2012 Volume 1 catalog) and Pocahontas (2012 Volume 2 catalog) ship, it's unlikely we'll see any of the more recently catalog'd sets from 2013/2014 being delivered.
Just my analysis... no inside information whatsoever. But something is clearly amiss with Lionel's overseas aluminum passenger car factory... which leads me to believe it may be even longer before we see StationSounds cars for all of these sets that were catalog'd without those cool diners.
David