Nikon has updated the already excellent 300mm f/2.8 AF-S lens with VR II (enhanced VR) and a Nano Crystal coat for reduced glare, and the least favored sibling of the Nikon TC family the TC-20E III...
The 300mm lens has been over-shadowed by it's zooming sibling the 200-400 but is blazingly fast and tack sharp. It is also easier to handle and less expensive than the 200-400mm lens, so it is a no brainer if you don't need the zoom range. It's also great to see an upgrade to the TC-20E. It has been the least favorite of the AF-S Teleconverters for most of us, as its larger size and slightly less sharp images than its TC-17E and TC-14E siblings have put it at the back of the pack. It'll be great if this new version brings it up to the image quality of its peers. I suspect its release with the new 300mm lens is no coincidence and that the combo will work very well together.
The new Teleconverter is about 1/2" (1cm) shorter than the current version and weighs about 1 oz. less. Nikon says it is the first Teleconverter ever to include an aspherical lens element (which Nikon says will virtually eliminate coma and other aberrations even at wide apertures). Interestingly the new 300mm f/2.8 is fractionally heavier than the current model and is listed as only focusing to 7.5' while the current version is listed as focusing to 7.2'. Nikon lists the new Teleconverter as not auto-focusing with their long f4 lenses but they are just setting low expectations--like the current version of the TC it will usually auto-focus at least with the center sensor and good light on the 500f/4 and 600f/4, although fairly slowly in most cases. You can learn more about the new 300mm f/2.8 VR II lens  and the TC-20E III online.