be suprised if there was a d300,. there's no need, nikon doesn't need a d300 the d200 is selling very well and there's not much that comes close at the price point,. there may be a d200s this year or early next which tweaks things a little
the next camera is likely a d2xs / d2hs replacment, whether they will keep 2 pro level bodies with different pixel count or change the crop factor who knows,. perhaps a d3 with choice of sensors switchable by the user
Sil