According to the official blog, the premiere of Code Geass: Boukoku no Akito 2 - Hikisakareshi Yokuryuu
was postponed until this summer. It was previously announced to be shown this spring.
Code Geass Akito official website
(new key visual)
Source: Code Geass official blog
EDIT (Jun 21, 2013)
The official website is now updated with the theater release date (Sept 14) as well as new information of mecha, characters and story. http://www.geass.jp/akito/