Nikon has just announced the successor to the D300s--the D500.
It has 3 times the auto focus points--153 and uses an Expeed 5-class processor to speed up things, up to ISO 51,200 sensitivity in the normal range, with a Hi5 setting equivalent to 1,640,000.
"Approx. 10 fps continuous shooting (up to 200 shots in 14-bit lossless compress RAW)" using XQD cards.
It has a sliding, touch-enabled rear display of 3.2 inches.
While it does Super35-compatible 4K video at 30p, it doesn't seem better than the Panasonic GH4 at this point, for video. (Apparently, the D5 does fewer than 4 minutes of 4K video?)
It seems like a great stills camera body, though. I wish they'd announced this in 2015, instead of the D7200. At US$1999.95, it's $300 more than I would have expected but the new AF module and better processor are likely worth it.
As I have the D7200, I would like to think that my choice would have been more difficult between the D500 and D7200, especially if the D500 would have been available in April 2015, and at US$1699.95.
I have not found the D7200 enough of a breakthrough model for me, nor the move (for me) to APS-C to be more than marginally better than micro Four-Thirds, unfortunately. I am pleased with the D7200 for wide work, but it is sufficient, not exceptional. Perhaps, hopefully, the D500 is exceptional.
Oh, and if you're wondering why there is no D400, it would have arrived at the same time as the D4, but they supposedly couldn't give it enough of a difference to create such a flagship DX model.
Update 2016.06.27: You've probably seen plenty about the D500 by now. It's quite tempting. It should be since it securely replaces a model from 2007. Although opinions differ, for me, it is the pinnacle of APS-C equipment, not the FujiFilm X-Pro 2.
I was quite amused that DxOMark used the Olympus E-30 as a model for comparison. Was there someone at the company who held tight to the E-30? Seeing the E-30 at 55 and the Panasonic GH4 at 74 shows how far micro Four-Thirds has come. I'm not sure I believe a score of 83 for the D500 and 87 for the D7200 because the D7200 doesn't seem quite so wonderful and the newer Expeed 5 class processor along with a slightly lower resolution should give better, not worse results. Then again, I don't really believe DxOMark numbers, except as a very general guide.
Update 2016.10.05: The more I think about the D500, I appreciate what it does, but wouldn't the Pentax K-1 do a better job, except for the speed?