Apple released iTunes 12.4 today. It features a significant UI change as well as updates under the hood. And AppleScript additions!
I've just installed it and note these AppleScript changes right off the bat:
current track - now recognizes tracks being played from "For You" and "New" sections. The tracks will be URL class.
download - originally for podcast episodes, now includes the ability to download cloud tracks or playlists to your library.
select - tell iTunes which objects you want to select (as opposed to selection objects already selected manually). [UPDATE: This is incorrect; see here.]
downloader Apple ID and downloader name properties of track.
New subscription playlist (an Apple Music playlist), miniplayer window and video window classes.
I haven't tested any of these very thoroughly yet. In fact, only current track. And of course, there is likely more stuff to discover. More as it develops.