The author clarified on my comment questioning that:
There is just no news yet that I have found, these codes came in as a surprise so I threw something up quick without a ton of digging. I'll look into the stages on NeoGaf and include that soon. The holding is for preview code and a date we can post. Not playing it yet since I didn't buy Ninja Gaiden, but man am I drooling to get my hands on it.