I suggest you go look at an current OLED display and reassess your opinion. Any kind of LCD requires some kind of backlighting for the colors to be seen, so you'll always get some light bleed somewhere. The best you can do right now is some kind of regional dimming that cuts the backlight to areas that are supposed to be darker, but even that has limitations.
OLED, like plasma before it, generates light from the pixel cells themselves. No backlight means no bleed. Something that's supposed to be black is black, not really dark grey. The colors also get generated exactly as they're supposed to since the backlight isn't washing them out at all. Deep blacks plus accurate colors equals a screen that really pops when it's fully calibrated. No backlight also means fewer layers in assembly and a lower power draw.
Easiest way to see this is to go into a cell phone store and look at the Lumia 950. It has a fantastic OLED screen. It's even better than the OLED on my older Lumia 925.