The rumors are getting too hot to ignore so this is a heads up to be ready for a possible Nikon update to the D300. The update is said to be called the D300s.
There is not a lot to report right now, but the Nikon USA site seems to be getting some work done to at this moment.
Here are a couple of links with some interesting information:
Nikonrumors and Photographybay.
We will be watching this daily to see how this unfolds. There is not a lot of specs on the camera but there is mention of an SD card slot.