Nikon has taken a huge step BACKWARD by omitting the 2nd card slot. They have taken a page out of Canon's playbook.
Reasons could be many - such as:
Now that Nikon has a flagship APS-C, and 8fps version with the same sensor would undermine that camera. This is the classic crippling tactic to push anyone with any aspirations to do pro work on the cheap up to the flagships. Want data security? Pay $2,000.
An apologist reason could be that the enthusiast consumer base that buys these, might not put 2 slots to use that much. This all depends on market research done. I doubt this conclusion. Anyone dropping $1K+ on a body in this day and age is more than an enthusiast.
In my opinion, due to cell phone camera advancements and the death of point and shoots - the new "enthusiast" realm is entry level DSLR.
Former "enthusiast" and serious-amateur DSLR's are today's entry level pro cameras. Canon and Nikon respond to this by ensuring certain time-saving and data-saving features are not available. A lot of people are making money with 60D, 70D, and Nikon D7000, D7100, D7200....
The move to a lower megapixel sensor is also a step-backward. Sure, on APS-C it's probably better to not have more MP as the sensor just can't get the most out of those megapixels. However, the 24MP Sony sensor in the previous generation is amazing. Perhaps the best APS-C sensor of all time.
I suspect they did this to up the FPS and more importantly, to use a Nikon design. This saves them money over paying Sony for their sensors. Sony does mark them up. They cut out this middle-man supplier and their profit taking.
This 20MP sensor isn't bad at all. It's actually really good...but it will always appear as a step back. It doesn't seem so on a camera like the D500 because that's a new camera and a 10fps speedster.
4K is BS. Just there to get on the specs sheets to compete. I doubt anyone creating quality 4K footage would choose this or any of the wannabe 4K DSLR rigs...
This camera is basically just cheap speed for Nikon users. Shame, the D7000 line was great. Trying to compete with Canon and following their steps is bad idea. They had addressed a need that Canon and others did not.
This is what happens in corporate shakedowns and restructures. They come in there and basically say everything they did was wrong, and then copy the market leader. That doesn't always work. In fact, it rarely does.
I'll be glad to pick up a D7200 on discount...amazing APS-C camera.