There is the ending for the black Taiki. That part is available in the novel "The Twelve Kingdom" by Fuyumi Ono. The book (English) is gonna be released in March 2007. I think if there'll be a warm welcome to the book maybe Studio Pierrot (which make this serie into anime if i'm not mistaken) and the author will decide to continue the story.
You can pre-order the book in Amazon.com also. http://www.amazon.com/Twelve-Kingdom.../dp/1598169467