until either edge detection improves or sensor-side phase contrast af makes its way into mirrorless, af and action photography will be lacking. But being that both canon and fuji have image sensors with hase detection, its only a matter of time, and frankly im suprised it isnt avaialable yet.
a as for low light and poor eyesight, that isnt a problem provided that lag can be addressed since the image in an evf is reflectve of the exposure. Focus assist and viewfinder zoom likewise help tremendously.
if avalanch photodiode arrays canmake their way into photography, then the dslr is done. Already the technology is used in scientific imaging, such as spectrometry. I suspect that in 10 to 20 years color avalanch diode sensors will replace cmos. At that point we can expect pmt performance on a chip. The SNR would be so high that, along with signal processing and display improvements, the optical finder would be vastly inferior.