Drudge has this up: "DEBATE COMMISSION HESITANT TO AGREE TO CANDIDATES' RULES... DEVELOPING..."
I'm extrapolating here, but I'm guessing that they don't care for the provisions Baker negotiated to help cover W's ass (no follow-ups, no direct questioning between candidates, "soft supporters" replacing undecided voters in the town hall format, etc.). If so, this would open up the usual "debate about the debates" that Bush bypassed this year and give Dems the opening to push the "is he scared of the people?" line.
That said, I don't see Bush giving in, especially with Darth Baker fronting for him. But this could add to the sense that the tide is turning back in the wake of the RNC.