Honestly, 3D is as much as a gimmick as "improved graphics" is. They're both irrelevant to gameplay mechanics, yes, but as RPG fans, we are very well attuned to the roll of atmosphere and immersion. Coming from the same community that gushes over Ico, Shadow of the Colossus, and Okami (myself included). These are 3 games that (among not being BAD in the gameplay category) are truly defined by their immersive atmosphere. Therefor, I think it's kind of hypocritical to discredit a technique that is designed to improve that very quality. One could define HDR Lighting as a gimmick too, but look how vibrant it made Shadow of the Colossus, or how enchanting cell shading made Okami. 3D is just another weapon for developers to immerse audiences in a game world in interesting ways. I have no doubt that many will abuse it and/or make it boring, just like so many HDR games these days provide little added feeling to the environment.
No, it's not an immediate game-changer like having a touch-sensitive screen, or analog stick. But it's an interesting tool that I'm sure will provide us with some incredibly enchanting experiences.