According to this tweet from advertising designer Uchikoga Tomoyuki, Gainax’s next TV anime project will be entitled, 「Panty & Stocking with Garterbelt」. It was originally announced at a 「Gurren Lagann Parallel Works 2」 TLA event. The main 「Tengen Toppa Gurren Lagann」 staff will be working on the series. More details are expected in the June issue of Newtype magazine — out 05/10.

[UPDATE 05.06.10] — New info from Newtype magazine:

*Synopsis

The story revolves around two angels — “Panty” (a blond-haired girl who wears teen-celebrity style fashion); and “Stocking” (a black-haired girl in gothic-lolita attire) — are sent from the Upper Region to battle against “Ghosts” on Earth.

*Staff Credits:

  • Director: Imaishi Hiroyuki
  • Character Designer: Nishigori Atsushi
  • Concept Art: Yoshinari Yo

[Source]