Board Thread:False Info and Speculative Discussion/@comment-25123326-20140727142854/@comment-4091815-20140727151820

He said (when asked about what should happen for Stiles in Season 5) -

"I don't know, end it with him getting bit and then... (gasp from reporter) Wouldn't that be crazy? (Reporter: "you'd be a wolf too.") Yeah, but then again it's like, I don't want... I guess... I don't know. It's so hard to make Stiles supernatural. On, like on one hand it would be so much fun. On the other hand I fight so hard for him to be the human always you know."

Nowhere does he say the fifth would be the last - he said that Season 5 should end with Stiles becoming a werewolf before walking that statement back.