User blog comment:Ḡwẵine Ḹٍٍkƨ Ĺiĸe Ͼềлȑềd/Series 5 will be the last! - unless we act now!/@comment-5209013-20120912091517/@comment-5209013-20120913081721

I don't know. They might also be present in later series.

I guess we'll have to wait and see :)