Lucasfilm has released a statement.
It has been cancelled... sort of.
While the studio is no longer producing new episodes for Cartoon Network, we're continuing production on new Clone Wars story arcs that promise to be some of the most thrilling adventures ever seen. Stay tuned for more information on where fans can soon find this bonus content.
Ok, so there will be more Clone Wars, just not on Cartoon Network. And the way they worded it seems to imply that future TCW won't merely be a new season on another network. Direct to DVD/Blu-ray? Online?
And here's the video from the link, featuring a scene from post-season 5 TCW: