Since mid-April 2016, not only new strings but also edits are synced between dev and stable (both ways, only approved translations).
When a plugin releases a new version all translations are copied from dev to stable. Credits would go to both users if translation (waiting or current) was created by different users.
If strings in stable are approved for at least 95% for a plugin/theme in a certain locale, the generation happens 30 minutes after a translation has been updated. Then any local WordPress set to use that specific locale will download it in the next hours after the generation.
Strings in readme are deployed almost immediately, but the 95% to reach is only needed for the strings of the plugin/theme.
If Meta projects (like Rosetta or o2) are updated, it takes between 24 and 36 hours before the update is visible.
(The WordPress projecst still need to reach 100% before they get created.)
If you as a plugin/theme author think your translators are doing a great job, then you can follow this PTE request process. You propose them and then GTEs from the requested locales can check further to verify that they are translating things properly. Most of the GTEs will start by checking what your translators already contributed and then see how to go further with them.
Every locale might have its own ‘procedure’ to nominate a PTE. GTEs want to ensure that no translations are just copied/pasted from something like Google Translate and that the PTE understands the language well. References might be made to existing glossaries and style guides to maintain consistency over all plugins and themes of the same language. You don’t want your plugin to refer to your admin panels under ‘people’ if it is called ‘users’ in your language. So some initial agreements are needed between PTEs and GTEs.
All GTEs are human and even have a life outside here. Also, not all teams have many GTEs (yet). So please allow some time to respond to your request.
Developers need an “ok” from translators to request that they become PTEs of their projects, but translators don’t need an approval from the developer to become PTEs for their projects. By adding their projects to translate.wordpress.org the developers are putting them in the hands of the translation community. Any contributor can request to become PTE for a plugin/theme by posting the request on https://make.wordpress.org/polyglots/ indicating the plugin name or link and the locale. An example:
Hello Polyglots, I have suggested strings for this [plugin/theme] and would like to become a PTE, can you please add me:
Name: [Plugin or Theme name]
URL: [Plugin or Theme URL]
If you have any questions, just comment here. Thank you!
If you want to download the latest available version of WordPress of e.g. the Dutch locale then you can use the following link that will always point to the latest one: https://nl.wordpress.org/latest-nl_NL.zip. Change the wordpress.org site and the ‘nl_NL’ to the desired locale.
After validating https://translate.wordpress.org/locale/locale-name/default/meta/wordcamp the WordCamp sites are automatically updated once a day at 00:00 UTC. In case of issues, post a message to the #meta-wordcamp slack channel.
Propagation is only available for plugins. When importing a .po, dev and stable are synced (both ways) and also dev-readme and stable-readme. There is no propagation outside the plugin where you perform the import.
The community here is dealing with wordpress.org translations. If you want to contribute to wordpress.com, then please check the FAQ on https://translate.wordpress.com/faq/ and place your request in the forum there.