AniDragon has headlines on a rumor thread on 2ch about an Angel Beats! 2 prequel anime based on the novel and
Originally Posted by AniDragon/Google Translate
For a few hours a great discussion was made in 2ch around some Scans (unaware of the magazine but can be Dengeki G's Magazine) where statements are made behind Angel Staff Beats! hacerca the project and which conveys the idea that it might be a second season. I must say that has not been told anything specific, let alone expect a confirmation of the rumor, there have been only hints about it.
Among the things discussed by users is stressed that the history of Angel Beats! can no longer continue that Jun Maeda has left clear that the Chapter 13 was the end, but it could be a prequel based on the manga "Angel Beats! Heaven's Door" or in the short stories of "Angel Beats! Track Zero published in Dengeki G's magazine.