Our sight is still, for most of us, our most trustworthy sense. Or, more accurately, the sense that we tend to put the most trust in. Modern neuroscience seems to enjoy mocking our trust in our eyes, with optical illusions and other tricks that fool the brain's amazing pattern matching systems. There's even a simple trick demonstrated by +Marcus du Sautoy where he asks people to assess the weights of objects of various sizes and, to a person, they all believe that the largest object is the heaviest, even though it is the lightest. So our eyes are easy to deceive.
What will 50 megapixel phone cameras accomplish that 5 megapixel ones can't? Well, it's not so much the megapixels, as the processing. Making a CMOS that captures 50 megapixels of light is relatively straightforward. The tricky bit is processing that many pixels and writing them to a memory card in a reasonable length of time. That needs a lot of processing fitted into a small phone. You could then do other things with that processing, like adding and removing objects, to a much more convincing degree than ever before.
Perhaps what is currently constrained to Photoshop and other relatively inaccessible tools could become more ubiquitous and easy to use. Perhaps there's a much darker side of ubiquitous photography yet to emerge.