I think he is discounting the creative options you can only have with an slr
What creative options are only possible with a SLR camera?
The SLR concept will turn into a niche market, just like rangefinder cameras. SLRs will dominate the pro market a bit longer, but eventually even there the concept of using a complicated mirror reflex system just to get a view through the lens will be dropped in favour of newer technologies.
Technology will advance and sooner or later live view will be good and fast enough to be a useful replacement for an optical viewfinder.
The biggest problem is probably the AF system, but with enough computational power in the camera even contrast detection could be very fast. Other solutions could be possible.