According to this latest post on AkibaBlog (NSFW), an anime adaptation of Fushimi Tsukasa’s light novel series, ｢Ore no Imouto ga Konna ni Kawaii Wake ga Nai｣, is in the works — produced by Iwakami Atsuhiro (”Kannagi“) at Aniplex. More details are expected with the release of the sixth volume of the novel — out May 10th.

*Synopsis courtesy of Manga-Updates:

Kyosuke Kosaka, a normal seventeen-year-old high school student, hasn’t gotten along with his younger sister, Kirino, in years. For longer than he can remember, Kirino has ignored his comings and goings and looked at him with spurning eyes. It seemed as if the relationship between Kyosuke and his sister, now fourteen, would continue this way forever. One day, however, Kyosuke finds a DVD case of a magical girl anime entitled Hoshikuzu Witch Meruru (Stardust Witch Meruru), which had fallen into the entranceway of his house. To Kyosuke’s surprise, inside the case, an adult video game entitled Imoto to Koishiyo! (Love with Little Sister!) is hidden.

[Source]