Yeah, headphones are no longer niche products. They need wider audience variety for still more high volume sales to justify crazy R&D for badassery. As for release dates, time between, etc, I am reminded of some book I read in college written by the CEO of PepsiCo during the cola wars, etc. There was a chapter addressing the time some idiot decided to "liven up" the recipe for Fritos. The punchline of the chapter is "don't fuck with Fritos".
The 580 was released in 92? 93? The 600 was released in 96? 97? The 650 was released in 02? 03? The 800 was released in 08, but is a true achievement in driver design and performance, and a very large step from the 580/600/650. The 600, 650, and 800 continue to sell well, and they are distracted selling weird shit to kids. So be it; I much prefer they take their time and get the next incremental advancement right. I am more disappointed they are spending so much money and energy hyping that stupid marble pet coffin.