According to the tweet of Uchikoga Tomoyuki (the president of CH Production), GAINAX's new anime "Panty & Stocking With Garterbelt" was announced at a live event of Gurren Lagann Parallel Works. The main staff of Tengen Toppa Gurren Lagann will produce the anime. The details will be revealed in this month's issue of Newtype magazine.

Director: Imaishi Hiroyuki
Character Design: Nishigori Atsushi
Concept Art: Yoshinari Yo

Source: Uchikoga's tweet

Updated on May 6th
Synopsis:
The Upper Region sends two angels "Panty" and "Stocking" to the earth in order to wipe out the prevailed "Ghosts". Panty, a blond woman in teen-celebrity-style clothes, and Stocking, a black haired woman in gothic lolita fashion, fight against peculiar ghosts.

Source: Scan of Newtype this scan missed the art.
7Th brought the art. thanks!