For Those Who Are Doubtful of a D300s Replacement

Why would they wait for Canon to show their hand? If Nikon had the D300s replacement ready, they'd want to make as much money as they can, and giving Canon time to provide a competitor isn't the way to do it.

Why wait for existing inventory to clear? On Nikon's Imaging Products webpage, you can still see, for example, both D5100, D3100 and D3k listed alongside the new cameras. Go to lenses section, and, same thing, old lenses listed alongside new. Nikon didn't wait to clear the stock of 50/1.8 AF to start producing the 50/1.8 AF-S. And so on.