Activision seems to be ready to present a new Guitar Hero prior to E3 (plenty of rumours of a reboot have been circulating). At least this is what is being suggested by an invitation that was sent out by Activision to media representatives in Germany. The mail states that an event is scheduled for April 1st 2015 taking place in "Hamburg Rock City". Among other things, the publisher would be happy if the journos would "rock the shack with us!" - a pretty clear indication that this is to do with a new music game and given the rumours of a new Guitar Hero...
http://www.gamereactor.eu/news/301694/Guitar+Hero+for+PS4+and+Xbox+One+announced+early+April?/