User blog comment:KID2NR/Second Season Confirmed/@comment-60.53.96.247-20130401033145/@comment-95.235.166.15-20130519102919

I think is more possible this way:

S1 taked the first story arc (Vol. 1 and 2) with 12 episode

S2 will take the second story arc (Vol. 3 to 6) with 24 or 26 episode with 6 ep (more or less) for volume plus the short story

for the second season we need to take present that from vol 3 to 5 there are 6 short story (during or after the event of the volume):

-short story 1 is into the vol. 3 time line and is "memory of oppai", before or after the event of kokabiel I don't know

-short story 2 and 3 are into vol. 4 time line and are "the oppai of tennis" and "hell teacher azazel", the first probably can be placed before the meeting and the second after the meeting since there is azazel

-short story 4, 5 and 6 are into vol 5 time line and are "300 Issei", "a tokusatsu devil" and "Issei SOS", don't ask me where they are in the time line because I don't know

S3 will take the first part of the third story arc (vol 7 and 9) with 16 or 18 episode (for this I'm not so sure)

for this season we have:

-from Vol. 7 time line we have the short story "the disturbance of a devil" and "the fun family of the gremory"

-between vol 7 and 9 we have the short story "the unsurrected phoenix" and "armageddon at sports day"

-from the time line of vol 9 we don't have (for what I know) short story, maybe they'll come out into vol 15, who know

S4 will take the second part of the third story arc (from vol 10 to vol 12) will take, maybe, 20 episode:

-actually there are only 2 short story, "The Worry of the Next-Next Heir-sama" and "an infinite shopping" (when Issei and Rias take Ophis for shopping)

notice that if they want to stop the anime they can stop here without problem if they want