How will WordPress 4.0 language installation work I…

How will WordPress 4.0 language installation work? I probably did not understand it fully, so I am asking:

1) Localized version will be ready several days after release of WordPress 4.0. Which language pack will receive new users in the meantime? Older (and complete) 3.9 language version?

2) There will be any button, that localization is complete or there will be many different translations? I do not want to allow not finished localization for distribution.

3) When I change some strings in GlotPress, all users will be automatically updated (every day)?

There are only 2 week to WordPress 4.0 release and there is no discussion with translators how it should work. And also no detail information 🙁