Razor's Edge seems to be a polished turd. It takes the elements from 3's slightly better predecessor that were removed originally, and puts them back in. Ninja Gaiden 2 was far from perfect. Ninja Gaiden 3 tried to go in a new direction and potentially be better than 2, but failed miserably. Now, this new iteration is essentially a 2-3 hybrid.
The new Ninja Gaiden series is essentially a type of game that actually has less to it than meets the eye. When one first plays the game, it seems a whole lot more deep and complex than it actually is. Even Black is fairly simple with moderate experience.
I'm really hoping for the best with Razor's Edge, but my expectations aren't particularly high. As you said though, it is nigh impossible that it will turn out worse than 3.