As you can see there is a wide range of opinions and all are probably valid depending on the priorities of the owner. Technically, the D7000 is better at all ISOs but mostly at low ISO where it is 1.5 stops better, with finer pitched grain-like noise. For image quality, the D7000 and for that matter the D90 before it which had the same DR as the D7000 from 200-6400. So in image quality, it is an upgrade by any measure: http://home.comcast.net/~NikonD70/Charts/PDR.htm This chart is by Nikonian's own Bill Claff who has researched this extensively. Select the models to the right that you want to compare.
But a sports camera is a normally judged on qualities other than image quality. The MultiCAM4800DX (D7000) is not as fast or sure in maintaining lock as the MultiCAM3500DX (D300s) but neither is as good as the MultiCAM3500FX. If sports, in decent light, is the primary subject, the D300s will perform more consistently.
Build quality is often judged on weight but with modern materials that is misleading. Neither the D7000 or D300 have a history of being fragile cameras and all the models from the D90 on have been tough and reliable while still being the best in their class for image quality.
Frame rate is another measure that is misleading. Shutter response time and blackout period tracking determine more whether one of a series of shots is closest to the peak action. The best shots are still the one anticipated for and timed and all after the first frame are a matter of luck. Newer cameras are getting faster in response time and are pretty good so that is essentially a draw.
The D7100 will complicate things greatly, with all the features most would want from a DX camera but with 6fps instead of the 7-8 from a 12 bit D300s. In the better 14 bit mode, the D7000 is 2.5 times faster than the 2.5fps the D300s is limited to. But most sports shooters compromise willingly on image quality and post processing flexibility in exchange for frame rate. For a general purpose camera in all lighting conditions the D7100 will be better, next comes the D7000 and then D300s In sports low light, the D7100 will trump both, particularly AF in low light with its -2ev AF sensitivity and low noise at high ISO because of the option of average canceling noise by downsampling. So, indoor basketball, the D7100 is the one to wait for. Outdoor basketball, the D300s will hold its own with acceptable image quality. The D7000 would be the bargain as it sells remaining stock deeply discounted with competent but not great action AF. If frame rate is most critical for you, which should not be an issue with basketball, the only real answer is a used D3s or a D4 however. It is designed for speed. For the price of a new D800, you can get a used D3s. While giving up quite a bit in IQ, it is a low light master and with speed enough for almost any style of shooting. Stan St Petersburg Russia