Hi artam!
Buttons in Playlist will be (almost surely) translatable in next build, only sections listed in ";changes" are translatable.
If you find a new section not listed in changes is (I think) only because the auhor has not yet created a check to that section, but he wants to remember of it in next build..
Regarding "old lng versions" is because BST release the program, and only then translators can translate it and post the updated file on this site.
Those translations will be available in next build..
Bye