The key word in your post is "if it makes them lighter." Frames are all made with alloys, so the weight of the pure metals is not the point. Note that titanium is used both in aircraft frames and in iPhone frames to make them both strong and light.I liked titanium in that it made the Pro phones lighter, but otherwise don't care much. I'd prefer aluminum on the Pro models if it makes them lighter. To me, that gives more of a real benefit than using a "fancier" material.