According to the official twitter, an OVA of IS: Infinite Stratos was announced to be released on Blu-ray Disc and DVD on November 25th. The title is "IS encore 'Koi ni Kogareru Sextet". The announcement was first made at the "IS One-Off Festival" event on Sunday.
More details will be announced on the official website, but the organizers were already taking pre-orders for the release immediately after the festival ended. The Twitter account also announced that the IS One-Off Festival itself will be released on Blu-ray and DVD on October 26. (Pre-orders at the event site for both the IS One-Off Festival and IS Encore releases would include an event art poster with reproduced signatures of Yukana, Yōko Hikasa, Asami Shimoda, Kana Hanazawa, and Marina Inoue.)