Tenchu already tried to maintain the same formula with Tenchu Z, Shinobido and Tenchu 4 for Wii and it didn't work out mainly because the formula didn't evolve. It was the same game over and over.. and I think it became quickly obsolete by the apparition of Assassin's Creed.
That sounds spot on.
It's impressive to see your game supports 6 languages. Is that a rarity with indie games?
Look forward to checking it out upon release. Best of luck with it.