It's an obsolete camera for anything but bright daylight subjects that don't require much cropping. That isn't to say that it wasn't state of the art in it's day, but so was a 1978 Corvette. The D300s does very few things that the D7100 doesn't,...and there are a lot of things the D7100 can do that the D300s can't.
Discontinuing this camera is a predictable development if the D7100 is to be the flagship DX camera. I'd say the chances that the D300s will be replaced with an upgraded "pro" DX body, which were already less than 50%, just went down by another half.
That said, if you want one, buying used makes much more sense at this point, even if you could get a new one.