It seems that there is still hope for the add-on (and maybe a possible fix for the achievement?!?).
First it was postponed due to JoWood going bancrupt. But word is that the add-on was almost finished prior to that case.
Now, in the German WorldofGothic forum a former JoWood community manager told that there are still plans for the add-on to be released and that we should wait until GamesCom in August, where the new ownership structure and further plans will be revealed. He called 3rd quarter of 2011 as a possible release date.
At least a spark of hope...