I most definitely want to see Derek challenged with someone in the cast like Wynonna. She is very popular, he is very popular, he is an absolutely fabulous, creative choreographer; however, Wynonna can not dance - she is not a Kirstie. Therefore, it would be an accomplishment on Derek's part to teach Wynonna and to bring her to the point of accomplishment that she deserves to be in the top 2 or 3 and not primarily on popularity on both of their parts.
If Derek could do that ( or something very similar - and Ricki Lake is not), then I would be satisfied.
It may not be in writing, but I suspect there is some kind of agreement that the talented, charismatic Derek will get a partner with some kind of evident potential. I believe the producers have a way of knowing who has some background and/or inclinations and how. They simply know stuff. This is their financial business, and it behooves them to know.