Just for the record, the superb D500 came out 7 years after the D300s, on 2016. From 2012 you can find hundrends of threads of Nikon fans demanding a new high end APS-C sport oriented camera. They felt they were forgotten by Nikon and many said they were considering jumping ship to other brands (with the Pentax K-3 being brought up quite often).
On 2016 CP+ D500 was announced and the Nikon officials were declaring:
"Was the D7000-series ever meant to replace the D300-series?
We were hoping that the D7000 series would cover a portion of the customer base that used the D300S, but the customers continued to say that they wanted a replacement for that model, so that’s why we made the D500." (source:
CP+ 2016: Nikon interview - 'the D500 is the D300S replacement that customers wanted': Digital Photography Review)
Now that might reminds you of something (K-3, K-3II, KP). Pentax is quite smaller and I feel that they are pushed by their base to release a K-3 succesor, as this was not their initial plan when KP was released.
PS: I feel that when the new APS-C will be released many ex-Pentaxians will sigh for the times they were shooting Pentax. How do I know? This is what history has shown so far. Pentax is slow in releasing new equipment, but most times it well worths the wait.