The official Twitter for the "Infinite Stratos
" anime series has announced that a new OVA is in the works titled "World Purge-hen." The final episode of "Infinite Stratos 2
" also included that the OVA will air sometime in 2014 which you can find here
The tweet also states that more information on the OVA will be given on the official site
at a later date.
Sources: Official Twitter
IS: Infinite Stratos - World Purge-hen