According to one of the head odoo developers the translations are migrated from launchpad to github about once a week and then they instantly become available.  The changes will continue to roll forward even after v8 has been officially released.  They used launchpad because the groups and infrustructure was already setup from v7.
Details on the translation process: 
https://doc.odoo.com/contribute/07_improving_translations.html

Synchronization (text from odoo developer)
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The new translations will be exported every day by Launchpad, but will only be synchronized back to GitHub every week or so - don't panic if you cannot see your translations in GitHub every day!  During synchronization the translations are of course merged back into a single project branch.

As usual, do not worry if you have not completed 100% of the translations in time for the release: updated translations will be included in the new installation packages every day, even after the release.  You can therefore focus on the most important parts first.

For the next release we will definitely have better tools for translators, let's just use the current tools one last time :-)

       Thank you all for making Odoo a unique and global project!