I also hate the milking of franchises.
But about Guitar Hero, it's just about new playlists...
World Tour added interesting functionnalities, so I wouldn't call it milking.
GH5 will bring us what I consider their best playlist yet...
What's bothering me more is that if you want to experience it fully, you have to buy the brand new guitar, and drums, and mic, each time...
All in all, IMHO people will get bored of buying full new games and accessories, so activision should stick with DLC, make it better, make it more integrated into the game, and make it cheaper. And release a new Guitar Hero when that really matters (every 3 years maybe)
They will know Helgan belongs to Helghasts







