Let's face it. The only people still playing Rock Band are the people are people like us on the forums, who simply can't get enough of it. People who love music, and love the feeling of playing along to their favorite songs on a video game. Sure, Rock Band 2 sold millions of copies worldwide, but a majority of players got tired of it after a couple years.
Let's take a look at Guitar Hero. The first game was released in 2006, which made a breakthrough for music video games because it was something no one had ever seen before. Then with the second and third games, the popularity grew and Activision was suddenly making tons of cash off of this franchise. But then, with Guitar Hero: World Tour not doing as well (and Rock Band 2 selling lots of copies), things started to turn around. So they thought "How about we start advertising the crap out of Guitar Hero, to get more people to buy it!" Guitar Hero 5 launched, and they didn't make back the money that they lost from all the advertising. A year later, Guitar Hero: Warriors of Rock came out, and despite its 93-song metal setlist, new storyline, exclusive Megadeth song, and Soundgarden tie-in, no one liked it and they had no choice but to end the series.
Harmonix was smart with Rock Band. Very smart, actually. By the time Rock Band 3 came out, everyone was sick of hearing about music games. People were done. They realized that the number of people that still played these games was merely a fraction of the people who had originally bought them. However, the people who still did play them were very faithful to the series, always buying DLC, posting on the forums, participating in online games, and more. So Harmonix thought "Hey, if we release a new Rock Band game, the Rock Band fans will know about it regardless of how much we advertise." It would have been pointless to waste money on advertising. So they didn't.
The game was completely aimed at Rock Band fans, and they weren't trying to reach out to the general public. They didn't take any risks like Guitar Hero did, like adding a strange storyline or advertising on every street corner. Notice how Rock Band 3 was not sold in a giant box set with all the instruments, because Rock Band fans already had those instruments. And this actually worked out very well for them. DLC is still a big money maker for Harmonix, and almost everyone who still enjoys Rock Band has paid money Rock Band 3.
Then Rock Band Blitz came out in August 2012. Two years after GH:WoR. People hadn't heard anything about music games for a while (except maybe Rocksmith, but remember Rocksmith is one player, Rock Band is more of a party game). People were ready for something new. And Rock Band Blitz was very new. The game is unlike anything people have seen before, and what's brilliant about it is that it reminds people that the Rock Band franchise still exists, but at the same time it's not the game with five colored frets on a plastic guitar that people were sick of by now. Best of all, you could play it with a normal controller, so they were clearly reaching out to people who had sold their plastic instruments, or otherwise just did not care about Rock Band at all anymore. If they had advertised Rock Band 3 more, people would not care about Blitz because they would be tired of hearing about Rock Band related things. This, I believe was the best business strategy for Harmonix. Try to sell to Rock Band faithfuls with Rock Band 3, then try to sell to the mainstream, general public with Blitz.
What do you think? Was there something Harmonix could have done better along the way? Do you think Rock Band 3 would have done well if they had advertised it?