Not true.
He can’t prevent anyone that received the code under the GPL from using (and distributing it) under the old license. He also can’t relicense code that he received under the GPL only under the new license.
If he receives a new license from the other contributors to distribute under a more restrictive license, he can do that because he has a dual license to the code and is not relying on the GPL for his right to distribute.
The most encouraging thing in the whole talk for me was when he told a roomful of IT folks that they need to join or form Unions and they cheered.