This years convention highlighted 1914 in several talks. They are going to hold on to it. To answer your question I think 20% would leave.
This is what I was thinking. I believe that anywhere from 15 to 30% of active JWs including ones with titles such as CO, elder, ministerial servant, either know and have investigated that there's something wrong, or have a very strong feeling that something is wrong. In 2010, there was 1,178,349 peak publishers in the U.S.. I'm assuming Western money is their chief cash cow, and if 20-30% of JW's were to be stumbled over them reversing this teaching on 607, or really any major teaching such as blood, disfellowshipping, Babylon the Great, it would have a traumatic effect on the other 900,000 who remained active in the US. Not to mention other educated coutries, such as the UK, France, heck even the countries in South America. It would be devastating financially, and emotionally if that many people, anywhere from a quarter to a 1/3, simply ceased being active JWs, it would be crippling. That's why, its never going to happen.
I have a glimmer of hope that it will considering them about to cash in on almost a billion dollars when they sell their land, and them creating a new headquarters in the middle of nowhere. They're getting prepared to weather the storm, and maybe they'll be sympathetic and leave it up to one's conscience on matters such as 607, Blood, Babylon the Great, the FAithful and Discreet Slave, etc.? Maybe they will, or maybe they'll remain the arrogant, refuse to admit their wrong, pompous assholes they've always been. Time will tell, I guess.