Wireless solution, please
I'd love to see Apple make a wireless solution that is better than existing Bluetooth headphone solutions. I wouldn't care if it's proprietary to iDevices, because that's all I would use it with. The problem I have with this Lightning headphone/concept is that you can already get very good to excellent portable headphones that were driven by the move to portable music players - Sennheiser Momentum, B&W P7, Beyers T51i, etc., etc. (but NOTHING by Beats). You can also get a headphone with a built-in amplifier (PSB MU4-2) that is really great (although it has meh looks and is heavy). And the iPhone already has a DAC and amplifier - Is Apple saying that the aren't good (or good enough)? Or that they'll downgrade those components in future iDevices to force people to Lightning-based headphones? This just seems to be a solution looking for a problem.
(I get it that hard-core audiophiles want something better than plugging a headphone into an iPhone with 256k files, but if that's where this is going, then you need, at least, to improve the source material, which most people won't bother because of file-size constraints. And then once you start down that road (DAC, amplifier, cables, etc.), you become a member of head-fi.org, and then it certainly will never end with a Lightning headphone.)
But a great wireless headphone - even if Apple-only - would be a potentially significant improvement over what it out there. I really like the Sony MDR-1RBT's (which I gave to a relative), and plan eventually to get another pair if something better doesn't come along soon. But if Apple really focuses on a solution that brings the SQ of wired and wireless closer together, perhaps with some iOS integration bells and whistles thrown in, then that's something I could get excited about. Still, the Sonys are so good (comfort, battery live, SQ, controls, etc.), it would have be a noticeable improvement. I've never noticed enough of a lag video soundtrack on BT to care, but others do, so for them, an Apple wireless solution eliminating lag would be a real plus.