Originally posted by Rondec I agree. Certainly Fuji, Olympus, and Panasonic aren't killing SLRs or the traditional SLR companies, even though they have been making mirrorless options for years.
Yes. But they haven't been very good. Electric cars have been around for ages... longer than petrol and diesel cars. But only recently have some of them become so good that they are a viable alternative. And they just keep getting better.
Would I take a mirrorless from 2 years ago? No. Not good enough. AF sucks, the EVF, if it even has one, has weird rainbow artefacts, is sluggish/lags behind and is low res, is bad at night, ... But that has changed. And it's only going to get better.
On the other hand, what advancements are possible for OVF cameras? PDAF on sensor? Not really useful, except for live view... essentially you have to turn it into a mirrorless camera. Bigger, brighter viewfinder? Not possible, it has peaked, unless we're giving up AF. Better PDAF in general... it'll always be limited by having a mirror only letting through a part of the light, with PDAF sensors on the sensor itself it's exposed to all the light.
Basically while mirrorless cameras can improve a lot, DSLRs can't. Here and there, sure. Slightly better AF, better sensors. But eventually mirrorless will catch up. Better AF, better viewfinder.