Activision had multiple "Hero" IPs in the works when Guitar Hero was ruling the world.
But when the bottom fell out of the music/rhythm industry and the annual take went from a few billion dollars to only a few hundred million, everyone started bowing out. Still, that doesn't mean a next-gen resurrection is out of the question.
Activision has managed to extend its trademark status for a currently unannounced project, "Sing Hero." The extension was approved on September 3; the publisher originally obtained the trademark back in 2009, at the height of Guitar Hero 's popularity. Of course, they've also registered intended IPs like "Drum Hero" and "Guitar Villain," but that doesn't mean the projects are in the works.
One spin-off, DJ Hero , did well for a little while, but the spin-offs, music packs, and competition from Rock Band over-saturated the market and everyone just sorta lost interest. Could "Sing Hero" be the virtual karaoke jam title of the new generation? Who knows?