Instead, ask why you'll need a phone when UI devices become invisible, ubiquitous, and networked.

Eventually, our children (grandchildren?) will laugh at our phone obsession. I'm imagining a silent reel of a Charlie Chaplin figure repeatedly patting all his pockets searching for his phone, dropping it when he does find it, pecking the wrong portion of the screen, and then when he finally answers the call discovering that the battery is dead. In other words, me, every day.