Earlier quoted context omitted.
Maybe not, but from the sound of it, a rewrite is necessary just to keep the lights on and to keep Thunderbird compiling in the long run.
What I don't immediately understand is why they can't just fork Gecko and continue using it for their own purposes. Apparently the needs of Firefox and Thunderbird have diverged, and Mozilla seem to have little interest in supporting Thunderbird any more, so is it a crazy idea to just separate the projects completely and avoid the whole issue indefinitely? Changing the UIs within this particular family of software pr…
If Thunderbird isn't updated, it will slowly die of bit rot.