It won't be on your phone by 2020. It is not clear whether it will ever be on your phone. The iphone 8 has about 3 million subpixels which will all have to be individually cut, tested and assembled on a display for a microled to work.

Or, alternatively, the display can be made from a whole wafer, which will cost about a thousand dollars for the raw materials and perhaps $5k for the finished display.

I know technology tends to advance a lot, but the advances required for microled to work seem really far fetched. Also, display technology does not advance as quickly as digital computation technology. Remember we have been talking about OLEDs for at least 20 years now and they are only now becoming mainstream.

This technology, if it ever works, will be for very small devices where brightness is very important but resolution is not that important. So smart glasses and smart watches. Even for those applications it is not at all certain that they will be able to bring the cost down sufficiently.