Sadly, I don't know when, but one thing at a time.
Ray Richmond at Past Deadline tells us that he was told by Lesley Cerwin (the publicist assigned to Studio 60, and the person to whom you want to talk when/if you call NBC to talk about the show) that work began on episode 20 last week. Since it makes no sense to pay for an episode you know you won't air, it certainly sounds likely that we'll at least get to finish out the season. Hopefully Aaron Sorkin will find a good final note to end the show on. While I still encourage people to call and demand another season, the odds of that happening at this point are, as no doubt you know, pretty well nil.
Stay tuned for further news of when the show will return. Still, good news, should Ray not be feeding us a line, is a welcome thing at this point.