As announced by Philipp two days ago the strings for the next Lightning release (1.0 beta2) have been frozen and you can now start to sign-in for this release.
We will be accepting sign-in requests until May 24 @ 23:59 pacific day time, so you have a little less than two weeks time to get your
locale in shape.
Lightning 1.0 beta2 localizations will be taken from the l10n-1.9.2 repositories, so please work from there.
If you have any questions, feel free to ask them in the mozilla l10n newsgroup or send me an e-mail.