I've thought about it before, and while a DBP project could pull elements from one of our jam sessions, I'm reluctant to focus a jam session around DBP.
The problem is the Dream-Build-Play is more of a long-term content, and the games created will have to be closed-source. Our goal (so far) with the jam session projects is for them to have a 24-hour commitment, and be completely open-source.
Of course, if everyone else is wanting to do something different, I'm all ears.
~Trey