I don't think 3D is a fad. It is a natural progression of technology where we're getting closer and closer to simulating reality. When I was playing Zelda on my 8-bit NES, my parents made the comment that it was so complicated. They were thinking video games would always be simple like pac man or asteroids. I wonder what they would say to something like Starcraft 2.
Movies. Was the addition of sound to a movie a gimmick? Color? Surround sound? It's hard to say yes looking back in hindsight, but they had their awkward moments.
Phones. Some would argue that the touchscreen was gimmicky.
That said, when a new technology first blossoms, it's often abused. When "stereo" music was all the rage, they put instruments solely on left and right channels (think drums on left, vocals on right) which gave a very imbalanced feel. These days, you don't notice the stereo. It now enhances the experience without hogging the spotlight. No one needs to market a song as "In Stereo" anymore. 3D will get there. It's just in that awkward phase where we don't know how to make best use of it. But devices like the Evo 3D are a necessary stepping stone.
Personally, I don't find 3D to be essential in my smartphone, but I hope to be pleasantly surprised.