The D300s is a very capable camera, and will remain so for years to come. Some seem to think its a must to have the latest and greatest. Anything announced at Photokina will likely still be months from shipping.
IMO it is better to let early adopters pay the most a particular camera model will ever cost, and be the real world, paid for the privilege, testers of new cameras.
It is somewhat of a canard that the price of used cameras goes down substantially when a new model is announced. Used prices may go down slightly, but it's rarely very dramatic.