Something new today that may help someone shed some light on this:
Yesterday (May 13) I checked my podcasts and they still had not updated. For some reason (desperation?) I tried to play the NBC Nightly News podcast for May 7th (the most recent one listed). But when the podcast played, it was actually the broadcast for May 13th. This evening, May 14th, I had "today's" podcast.
CBS News' podcasts are also now there through yesterday, the 13th (as of about 7pm PST), however the sequence of episodes is out of order for some reason (not a problem).
The CBC National (Mobile edition) is also up to date.
I'm glad it's resolved, but Apple's silence on the matter is deafening... even if they put out the word that "there's nothing you can do and you just have to wait for it to fix itself" it would at least show that they're aware of the issue. Disturbing.