Didn't this fad fall off when there was a new game every 5 to 7 months? Between Rock Band and Guitar Hero there was just too many of these damned things.
Rockband was more of a general hub where you could bring over the songs you bought from the music store as opposed to Guitar Hero where every new iteration was it's own setlist and you couldn't amalgamate them into one engine/experience.
Bobby Kotick, was the same motherfukker that got in and literally told them "Exploit it" and there was a Guitar Hero - Anything, where the market got super sasturated with content plastic peripherals to the point it lost flavour quickly.
Rockband atleast tried to keep the music you purchase/had in an all inclusive package to a certain point, but by then the ship had already sailed and the casual folk moved on/got tired.
I'd rather see a new rock band that incorporated Two guitars, a bass, Drums and keys so that people wanting to play in a fullscale band would be a thing like what Rockband 4 tried to do.
The online section would definitely open back up if that were done properly like it was back in the day when It was easy/fun to pick songs and play with randoms and try and beat/play it over voice chat.