At long last, the venerable 80-400 AF-D gets an update....ouch look at that UK price though! Wex have it listed for pre-order at a shade under £2500!
Even though the price will soften, it probably still makes it worth looking at the 70-200mm f/2.8 VR II as an option - after all a 70-200 and a D7100 are in the same ball park, price wise, as the 80-400. You would still get the equivalent of a 140-400mm lens using the 15Mp 2x mode.
Add to this that you'll be able to shoot 2 stops faster, i.e. brighter viewfinder, more subject isolation, potentially better results with a teleconvertor, faster AF, as well as a higher shutter speed (remember VR doesn't help you avoid subject motion blur).
Personally, I can't see much reason to buy the more expensive lens - unless you really, really need lots of reach and will combine it with a D7100 to give a very portable 160-800/5.6 equivalent!