What the hell!? If there is no backtracking, then aren't we returning to the oldest format of the game design in which we go level by level? No matter I' still getting the game.
According to Nintendo Power, you can backtrack to places you've already been, but there's not as many secret areas and such.
Personally, I think Castlevania NEEDS to go back to a level-by-level format, which is where it really shines. It can be just as dynamic as MetroidVania style, as seen in games like Dracula's Curse and Rondo of Blood. Level-by-level can have alternate routes that force you to make a decision and stick by it. (The meandering of the MetroidVania style ticks me off at this point; there's no sense of driving forward). A level-by-level format also allows for more levels with rising water or destructable environments because you don't have to backtrack and thus the level can morph drastically and provide a variety of challenges. Plus, CV64 demonstrated that level-by-level can still have adventure elements of finding items, hitting switches, etc.
This OOE still doesn't feel like it's level-by-level, as each smaller level seems to be a mini-MetroidVania. By and large, I don't think this is a huge departure from the SOTN-types. In fact, it sort of seems like SOTN mixed with Megaman ZX. (At the very least, I'd hope for a compromise by now. With self-contained levels that you can return to, there's no reason you couldn't mix the old level-by-level format's environmental strengths with SOTN-style. But this appears to have missed that mark, as it looks like you're just fighting enemy after enemy without really dynamic level layouts).