It's been a long time since I looked into this stuff in depth so I may have some details wrong. You are incorrect about the importance of sensor size. For a high quality image I'd prefer a larger sensor over a small sensor with more megapixels. For one example where small dense sensors are worse look at noise in the image. As the pixel density increases each pixel is getting hit by fewer photons. This reduces the true signal so your signal to noise ratio goes up.

Based on the use of Foveon sensors and light field tech from Lytro I wouldn't count on lens less cameras showing up in a phone in the next five years. A decade wouldn't surprise me but it's hard to predict tech trends that far out.