Ninja Gaiden Sigma's director, Yosuke Hayashi, was kind enough to take questions from members at the Official PlayStation forum. His Q&A results are in.
His comment about DC was pretty intriguing:
Q: Do you guys plan to take advantage of PSN and add downloadable content similar to what you did with the Hurricane Packs?
A: We'll be making an announcement regarding our plans for downloadable content soon. The content will have some amazing depth for a download!