According to an Activision rep, the company will continue to support Guitar Hero Live, which is an ongoing, online-focused service. "Activision Blizzard remains fully committed to the UK games industry, and our teams based across the UK." This presumably means that another British developer is learning how to manage the game.
A couple days ago, Activision support tweeted that they are investigating the case of the missing premium songs.
Let's wait it out until July 31 to see who's right.