ReallyRightStuff sent out their 2011 catalog today and they have a entry for a new BD4 or BD4-L plates for Nikon D4 camera. The comment section says "Camera to be released mid 2011. Check website for plate details":
The wide spread belief is that Nikon does not share information in advance with different vendors about unreleased cameras. On the other hand RRS is a serious company with excellent products and I am not sure why would they speculate on a future Nikon camera in their official 2011 catalog.
P.S: dpreview's review of the Nikon D7000 is up (overall score: 80%, D300s had an overall score of 82%)