Its done when its done!
The public beta already starts.
If you buy now a license, it is valid for Sublime Text 3, and includes all point updates, as well as access to prior versions (e.g., Sublime Text 2). Future major versions, such as Sublime Text 4, will be a paid upgrade.
If you already bought a ST2 license in the past, i think it will be a small upgrade fee for older st2 users.