We've been discussing the l10n status of the TB 3.1 beta2 release internally. We have come to the conclusion, that due to the high number of late-l10n checkins, we need to extend the l10n sign-in deadline by three days. That should give localizers more time to adequately test their localization.
Therefore the new sign-in deadline is: Thursday April 29th 23:59, pacific time
Please use the new sign-in functionality in the l10n dashboard to become part of this release with your latest revision.