A scan of the upcoming issue of Dragon Age
magazine revealed that an unaired episode, tentatively titled Yomigaeranai Fushichou
(The Unresurrected Phoenix
), will be bundled with the High School DxD
DX.2 light novel volume. The novel and bundled Blu-ray disc will be released on December 9, 2015.
The third season, High School DxD BorN
, is set to air on April 4.
Source: Scan via ANN