A reliable news from NR said: the upcoming Nikon D300S replacement will be named Nikon D9300. Not the rumored Nikon D400 or Nikon D7200 before.
Nikon D9300 will be a DX body and will obviously be placed above the D7xxx line (Nikon has probably decided to keep the Dxxx line for full frame cameras and Dxxxx for DX bodies). In order to match the version of the D3300 and D5300, Nikon will name this as D9300 instead of D9000.
via: NR
Read more: Nikon Rumors