According to Shingeki no Kyojin
volume 14, spin-off manga Shingeki no Kyojin: Kuinaki Sentaku
will get an OVA adaptation, to be bundled in volumes 15 and 16 of the main manga to be released on December 9, 2014 and April 9, 2015. This spin-off manga features Levi
as main characters.
Source: Preorder Notice Page via ANN
News submitted by keragamming
Shingeki no Kyojin: Kuinaki Sentaku