There are 200 songs on this spreadsheet that have been mapped with difficulties, and not adding them would be a major waste of money. Because GHTV is an ongoing service with Activision itself supporting the new additions, taking over from where FSG left off.
One user [not going to mention their name] is extremely certain that the metal show will be the final update, as it was the final setlist with time stamps. [The premium shows are now updating once a month and run for three weeks each. The fourth week is presumably a time where Activision Publishing seeks out a new monthly show.] There may or may not be a July show.
From the looks of things, the May/June charts and songs were made and selected by Activision itself. This means that either Activision will ignore the songs in the cache, or they will select different songs.