yeah the anime of zero just left so much stuff out compared to the light novels that they trap themselves at s3, now if they want to make a 4th season the 1st half will be like a jigsaw puzzle trying to fit important plot devices into the story that should of been there ages ago.....
anyway about shana3 they better follow the LN,
id rather watch the LN version instead of some series packed full of swimsuit fillers especially after waiting for years for another season