Coto told IGN that the Showtime drama will be "a different show" following Deb's (Jennifer Carpenter) discovery that her brother Dexter (Michael C Hall) is a killer.
"It will affect their relationship from now on," he said. "It's not going to be the same... which is a way to refresh and remain creatively alive."
He continued: "[We had to] change the dynamic, and change the show. Now it's about a serial killer who has a sister who's a detective who has found out that he's a serial killer. She has a big decision to make this next season."
Coto admitted that it is a "terrible challenge" keeping Dexter fresh, adding that it is necessary to keep reinventing the show.
"It's the hardest thing there is to do," he insisted. "The only way to do it is to overturn the apple cart every once in a while. And let the characters grow and progress and have their lives get overturned."
Dexter was picked up for a seventh and eighth season back in November.
Earlier this month, Showtime's entertainment president David Nevins indicated that the series may also continue into a ninth year.
Dexter will return to Showtime in late 2012.
> Dexter writers considered season six storyline twist for years