Come on Comcast you are letting a lot of your customers down. You published the availability of Season 3 until November. Now you say PBS won't allow it. Why wasn't availability assured before you advertised it to us. Pull some srtrings, "lobby" with PBS. Do something..we want Downton Abbey season 3, Counting on you..
Given the information in the existing thread at http://forums.comcast.com/t5/Video-On-Demand/Downton-Abbey-Season-3/m-p/1653319 it seems that Amazon got the rights to it and as part of that it might very well be that other providers lost their rights. Strings or no strings, probably not much any of them can really do if that's part of the agreement (or its consequences) between Amazon, PBS, etc.
As for the availability date, yeah, seems like there was an unfortunate problem with that--either Comcast got it wrong and put an incorrect date originally (which is a small mistake that can definitely slip through) or the new Amazon deal changed things in the middle of it all, and there really wasn't much else that could be done (which is still unfortunate, but it's just reality).
Not a consolation but it may help you in the future. Yes when you looked at the overall DA Season 3 guide, it did say the expiration was November 2013. However, if you drilled on any individual Season 3 episode but using "INFO" on your remote, you would have gotten the individual synopsis of the program and would have seen that YES, the expiration was April 3 or so. I was ending Season 1 and yes this was the case. Watching it on streampix was nice as it was a bit cheaper and more efficient to watch.
However, when done with streampix, easy to cancel and not paid for UNUSED DAYS.
Season 3 is available with itunes, amazon, or vudu for $19.99; yes the stepup in price in obnoxious.