Wouldn't all previous releases be fork-able under the terms of the current GPL in that case?

Yes but it would potentially split the community.

Agreed... that was my point. Specifically, it doesn't matter who takes over or what the changes are, only that direction/priorities may change and be inconsistent with the intent of the original contributor.

The existing code cannot just be "re-licensed". It's true that they might decide to make future versions available only under some weird license, but that wouldn't cause prior contributions to become unavailable. Continuing the code line under the original license would always be possible, given effort.

That's when we fork emacs with the GPL license. You can't retroactively change the license to the code you published as GPL before