I don't think it matters so much what Amazon does with 3D sensing. If the phone has this capability, good developers will find many innovative ways to utilize it. I think it's a good addition. Hopefully Apple is working in this space.
However, six cameras is a lot of space to use up in a phone. My guess is that Apple will come up with a more elegant solution and provide the same functionality in a smaller device. It may take them a few years longer.