Another Ray Franz type incident would be catastrophic in this age of media and the internet. Back then, his book caused some shockwaves I imagine. I was a kid then, so I don't remember what happened. People my age still in, and younger have never heard of Ray Franz. I don't believe most JWs could name you five members on the GB or who the President of the WTS is. Some couldnt even tell you who the Service Overseer or Secretary is in their own congregations.
But, if a charasmatic dissident in NY decided to make a play, it would be huge. There'd be no way to keep something like that quiet without collateral damage. That collateral damage would turn into more disillusioned and eventual x-JWs. All because of the spread of information via the Web, and I'm sure if Time Magazine had articles on Franz in the 80's, some major media would cover a modern dissident.
A major core teaching could cause some problems. I don't mean a "this generation" either, as previous posters mentioned, most JWs couldnt explain the past two or three interpretations of "this generation." It's really not that important to the average JW. No, it'd have to be something that would put more pressure on current JWs to make them break, or something so outragous that even Corky would know somethings not right.