You're misunderstanding what Retina Display is about. Apple does not use the native resolution as the default resolution, it will use the HiDPI resolution (2x) by default.
The font size stays exactly the same except it will be twice as sharp, it will actually look like you got a new pair of eyeglasses.
The native resolution of the panel will be at 4096 x 2304 but the default HiDPI/scaled resolution will be 2048 x 1152 (4096/2 x 2304/2).
People with worse eye vision will actually benefit more from Retina displays.
Thank you for that. I must note that I don't have a retina screen, but noted no discernible difference between 1280 v 1680, in sharpness of fonts (graphics do not matter to me). However, it does beg the point - why pay for twice the pixels than are of use to me?