A lot of sources on the net keep mentioning that Igarashi says that a PSN version can indeed be made. Kris Pigna from 1UP had an article (last June) [http://www.1up.com/news/castlevania-harmony-despair-psn] that quoted Igarashi, saying that he's just "focusing on Xbox Live Arcade," and that "there might be a possibility with [a PSN release of the game]. I hope this one sells, and then we can think about PSN." 
So those of us with XBLA friends...pimp this game out to them pronto, so the rest of us can start playing this awesome game!