Anybody know when High Schoo DxD Episode 15/ OVA 3 is coming out?

I recently looked at the High School DxD OVA page at myanimelist.net. It says the OVAs are episodes 13, 14, and 15. I was surprised because being the hardcore fan I am of the series, I have no knowledge of Episode 15. There is nothing on Wikipedia on it either. I am assuming some time in the near future it is going to come out with a manga book, if it hasn't already done so.

Does anybody know its release date?
Or, if it already has came out, does anybody have a link to where I can download it?

http://myanimelist.net/anime/12729/High_School_DxD_OVA