It’s going to be awhile, but there will be more Watamote after the twelve episode series ends this month. The manga will be bundling an episode 13 with it when the seventh volume is released on October 22nd, 2014. So yes, a full year away. The episode is being done by the same team as the TV series as it’s basically being considered an unaired episode and it’ll be part of the limited edition bundle with that volume from mangaka Nico Tanigawa.
The manga is being released domestically by Yen Press while Crunchyroll is streaming the series. Sentai Filmworks has the domestic home video rights for the series with plans to release it sometime in 2014. The OAD episode is highly unlikely to be considered part of that license agreement.
Yen Press is publishing creative team Nico Tanigawa’s manga in North America. The television anime adaptation of the manga premiered on July 8 on the TV Tokyo. Crunchyroll is streaming the anime as it airs in Japan.
Series Concept: The protagonist, Kuroki Tomoko, thought she would naturally become popular once she became a “high school girl”, but reality was different… Tomoko panics at her situation and decides to take action to become popular. But… she doesn’t stand out in class, she’s extremely shy, and bad at communicating with others so she has to start by talking to someone other than her family first… The unpopular girl, “Kuroki Tomoko” fights her hardest to become popular, but… Does a bright future await Tomoko?! The struggles of an unpopular girl start here!! less
[Source: ANN]
I don’t necessarily consider the OAD episode being completely out of the question when it comes to the Western release. When Steins;Gate was released on DVD/BD, the special OAD episode was included.