I think it was a genius move on his part . u_u
That it was. If Jiraiya continued living, he would have no relevance to the story and just be overshadowed by other characters, the same way everyone in the K11 were, bar Shikamaru.
ot: Lack of development on characters in the K11.
Making the war arc too long.
Not killing Hinata...given the way he is currently writing her character.
He also has stated in past interviews that he doesn't always plan ahead & that he wishes that he did because it would make it easier for the story to remain consistent and avoid plot holes.