Great article. It's good to know that Harmonix can still be humble and forthcoming about where the market interest for rhythm games is right now and what they can do about it.
I've considered myself a die-hard Harmonix fan and Rock Band player. Through '08 and '09 especially, I kept current on nearly all the DLC and played each song as competitively as I could on guitar. I was one of those people who would systematically play a song 10+ times in a row to "squeeze" more points out of them. I really did enjoy that process; listening to, and being exposed to, a lot of new music. I continued to buy the majority of the DLC up until the launch of Rock Band 3, when I totally hit a wall and burned out on everything.
It's a shame, because it's really no fault of that game or Harmonix's split with Viacom that it happened, but it was the endgame of the formula of content oversaturation. Looking back at it as a competitive completionist, there were a lot of songs I bought that I could've done without. Going into Rock Band 3 with all that content, wiping the slate clean with my scores, having to figure out new overdrive paths for everything, all while trying to wrap my head around Pro guitar and keyboards, somehow turned Rock Band into something that was rather stressful, not as fulfilling to me, and had a lot of "baggage" involved.
Rock Band Network was a similarly exciting prospect that I think has fallen victim to over-encumbrence. I know that the core fans who work on that stuff work really hard, and deserve all the praise they get, but the laboriousness of it all still tends to create a "gameplay first" environment where certain genres are more or less left sitting in the queue.
I'd love to see Harmonix come out with a new IP that doesn't abandon rock music, but is perhaps a more focused, creative experience that concentrates really hard to enhance a super-cohesive and personalized assortment of songs. Harmonix doesn't even need all the peripherals and 1-1 note correspondence simulation gameplay to create a quality experience. They need a concise, fresh tangent to recapture that spark with people. That said, it's great that they're thinking about reinventing Rock Band while continuing support for DLC, because at this moment the pace is hardly compelling enough for anyone.