It ended after an abbreviated season 6. However, they had season 7 (and maybe even 8?) planned.
As an aside, what did everyone think about how they dealt with Ventress in the later seasons? They seemed to be trying to make her into a sympathetic character, but after all the evil things we've seen her do, it just didn't work for me. Explaining why she is the way she is would've been fine, but I think they went too far by trying to make her sympathetic.