OK, I will play a mirrorless advocate here.
I think CaNikon will be soon in dire straits with their cropped DSLR ranges and huge legacy of DSLR cropped lenses.
If we look at the dynamics, mirror less are moving so much faster than the slow, incremental changes in DSLR world. Things that yesterday were a disadvantage of mirror less are rapidly becoming its advantages over DSLRs.
Just two years ago EVFs were clearly inferior to any OVF. Now, I believe X-T1 has changed the game completely, it's huge, bright, fast OVF is superior to tiny, dark cropped DSLRs OVFs, and all of a sudden we see added benefits of an EVF - close ups, focus peaking, split focus, split frames, you can open the menu right in your finder, you can see the shot how it will look, you have virtual instant metering etc. ... It is just a better technology.
DSLR are trying to make advances in cont. shooting speed. An added frame or even half a frame per second is a success. Because there is a bloody mirror that has to go up and down! With mirrorless, that is not hampered by a flapping mirror, 8, 10 frames per second is already nothing special. Expect 20 f/s soon. Now, what DSLR will have for an answer to that?
DSLR are still hanging on a better AF, but mirrorless are catching up with frightening speed.By the end of the day this is all about the brute force of a faster CPU, and CPUs,as we know, have strange tendency of getting faster every year or two. Plus added advantage of focusing straight on the sensor, without any focus mirror, need for calibration, back/forth focus issues etc. So the writing is on the wall here as well.
Next - lenses. Nikon has decent DX lenses range. Good, solid glass, albeit nothing like WOW. Can it compete? Well, mirrorless lenses have shorter flange distance, that means for the same APS-C sensor it is possible to produce slightly smaller, slightly lighter and slightly better quality lenses of the same manufacturing costs. We see excellent MTF glass and FUJI X-mount APS-C is another example. So economically mirrorless lenses FOR THE SAME SENSOR have a strategic edge. That means, sooner or later the huge advantage of CaNikon glass legacy will turn into a huge stone on their necks. Unless they bite the bullet, ditch it mercilessly and start producing their own mirrorless DX glass for their own mirrorless DX bodies. Judging by their suspicious unwillingness to add new fast DX lenses, they are already thinking about it.
Batteries with mirrorless suck compared to DSLR. Thanks to our Chinese friends we can have pockets full of el cheapo batteries these days. Probably, when mirrorless seriously attack the pro market, they will start manufacturing larger bodies with ample space for added/larger batteries. And added grips, like X-T1 does already.
The mirrorless technology has not yet matured, but it is maturing VERY fast. Still it is not quite here yet. That is why we see all those funny little bodies andfancy designs aimed at amateurs and tourists. Even those companies who marketed their cameras for pros, like top FUJI and full frame Sony, in reality do not aim at professionals at all. But as soon as technology is matured enough - and judging by the pace, it will happen soon, - mirrorless will attack the professional high end market mercilessly.
How exactly will it happen? Well, imagine a modern supersonic jet attacking a good, solid WW2 film era fighter equipped with two lovely propellers and a flapping mirror in between.
I predict: flat bodies with Huge screens, changeable grips and very large EVFs with all bells and whistles, 20-30 ("Do you want faster? Really? We have faster, Sir".) frames per second cont. mode and up to 1/30,000 sec electronic shutter speed, fast hybrid focus systems, probably even separate CPUs for display/EVF and focusing/shooting/processing, etc etc.
So as I said cropped DSLRs will soon get in serious trouble. The question is ladies and gentlemen, what is so special about Full Frame DSLRs that makes them feel any safer?
DISCLAIMER: This speech, ladies and gentlemen, was of course a bit tongue in cheek, and by any measure was not a dig at current DSLR cameras, that are beautiful pieces of modern engineering. Whatever happens, it will still keep producing wonderful images, especially in the hands of honourable members of TPF.
DISCLAIMER TWO: As English is not my first language, I always hesitate to write long boring posts like this one, so if some phrases sound weird, give me some slack, will you?