Think about it.
When Kanade disappeared from the afterlife we don't know how long Otonashi stayed there by himself as the new Student Council President. We do know that he eventually moved on himself as shown by the after credits scene where he reaches out to Kanade in the Real World, but we know that time doesn't factor into Afterlife. (Shown by Kanade being in the afterlife long before Otonashi even though she died in the real world after He did.) So, this means that we could have a second season about Otonashi helping people move on as he waits for whatever he was waiting for. I personnally think that he was waiting for his sister Hatsune, so that he could make sure that she moved on before he did.
Opinions People! What do you think?!