I really think it's going to be OK.
When they first introduced Lightning, Apple was careful to describe it as a multi-protocol digital interface. I take that to mean that on the phone end, the interface chip can be software-driven to emulate things other than USB (and that what people call a "DRM chip" in Lightning cables is more importantly a handshake chip, that tells the phone "I'm a USB cable, so use that emulation mode").
So, if the interface doesn't have to act USB-like, and if Apple still wants to bundle cheap-to-build iBuds with phones and iPods (and sell other earwear too with the best possible margins), what are they going to do? I figure they will supply at least one audio mode that is very cheap to build for. It seems to me that would be PWM, plus the chip for handshake and the control signals (play/pause, volume up/down).
It seems to me that in that case a minimal adaptor could be small and cheap, either sold as an Apple accessory or provided by headphone manufacturers in the "designed for iPhone!" editions of their products.
And none of this precludes higher-fidelity DACs and pro-level digital audio protocols for them. I think Apple gets a certain amount of mileage from showing people using iPads for mixdowns and performance and DJ-ing and the like, so I think they will make sure there are pro-level Lightning audio protocols as well as an audio protocol optimized for inexpensive iBuds and the like.
Just my speculation.