The point I'm making is that it is ok to find the HD800s sterile, bright and lacking euphony because this is how they sound when using "wire with gain" equipment. They are what I'd consider "true reference" headphones in that though they have too much treble without EQ, they didn't compromise on their design so it matches peoples subjective tastes. Whether a reference headphone sounds good is irrelevant to the design goals of a reference headphone. Reference headphones are meant to reproduce the signal as accurately as possible and for many people here they don't like how that sounds. That's understandable and there is nothing wrong with that. So people use amplifiers to change the signal to something they find more enjoyable and that's fine. I just think it's important that when people say X headphone needs expensive amplifiers they add the caveat that they need expensive amplifiers to produce a sound more enjoyable to them. You don't need super expensive equipment.
I'm sure that the engineers at AKG didn't care how good the K812s sounded out of a portable media player, the high sensitivity wasn't a design goal but came about as an additional benefit while they tried to make the best reference headphone they could out of their constraints. I don't think that there is any desire for people to make highly sensitive reference headphones as long as they don't cross over into HE-6 territory.
I doubt there is a "new generation" at all outside of orthodynamics where sensitivity and weight are huge concerns. Sennheiser will release some electrostatics that will probably be technically better than the SR-009s which will be great for everyone except Stax. Dynamic headphones will generally stay the same as the technology has hit it's peak for the moment. Audio companies will try to market like Beats with mixed success. Perhaps, audio companies will try to build a marketing bridge from the $400 range to flagship level home audio in the mass consumer market. I'd be impressed if they succeeded. AKG will probably try and build a newer K812 that performs technically better.