Sadly, there is no record on when the second season of Downtown abbey will be available on Netflix. The date is yet to be announced to the public. You need to keep checking on online sources to get any updates.
I just got off the phone with Netflix and they recorded this request. They do actually track this stuff. More importantly, they said to go to instantwatcher.com (a 3rd party partner of theirs) where you can see expiration dates, upcoming availability of stuff, and make requests. They also said you can use the "blog" button at the bottom of the home page (it's nearly microscopic, but it's there). I say let's flood them with DA requests until we get it!