Nikon USA has already made the 5 years old Nikon D300S as an archived product.
According to latest rumors, the successor of D300S will not be called Nikon D400, instead, it will be called Nikon D9300. Nikon D9300 is rumored to be announced in this summer, to compete with Canon’s 7D Mark II.
via: NL
Read more: Nikon Rumors