Good news, for localizers. With the new release of the l10n dashboard, co-developed by Pike (Axel Hecht) and Gandalf (Zbigniew Braniecki) we're killing off the opt-in threads for localizers.
Every localizer should take a close look at all the functionality that the new dashboard exposes. There is also a 5-minute screencast, that hopefully guides you through some of the new features.
We'll start to use this new functionality once Thunderbird 3.0.2 is out of the door. So Thunderbird 3.0.3 and onwards as well as Thunderbird 3.1 beta1 will be our starting points.