Certain parts used in construction are no longer made.
The official reason was that the equipment needed for production has worn out.
The subtext was that they weren't selling enough of them to justify keeping them in production.
Mind you, the K-1000 was a modest seller, often heavily discounted, and a very controversial headphone here. It got the same "no bass" moan the HD-800 does. (I think the bass is excellent on both, for the record.) Some chuckleheads around here would plug it into an OTL with an output impedance higher thsn the K-1000 and lousy power output, then crap on the K-1000's sound. Of course it sounds bad if you're an idiot and plug a K-1000 into the wrong thing.
The amping part got sorted out here over the past few years. Almost everyone knows that the K-1000 needs speaker-type power. I have no idea how the misconception kicked off - the K-1000 manual tells you in no uncertain language what it needs.
Anyhow, my point is that the original got trashed regularly while it was in production and didn't sell well enough to update the machinery. The suits are unlikely to do the same thing again.
My fear is that we'll get a warmed-over K-701 driver in an earspeaker style, or maybe in some blingy aluminum cups. I have serious reservations about what AKG is capable of today. Dayglo celebrity vehicles are not impressive. I can almost see thir engineers cringing.
Even worse is how poorly voiced the K-701 is. A lot of people find the mids unnatural - I cannot believe this didn't turn up in testing. They had to have known it was "off" from at least a few people before starting production. I wonder if AKG will make another mistake like this. Also interesting is whether another viral campaign will follow - the K-701 seems to turn up with celebs more than it ought to.