I for one think it doesn't matter all that much. Most people who have invested in fancy headphones either don't use their phones as a source or use a DAC in between. Companies that make USB DACs today will start making Lightning DACs and it'll be great. I agree with Irvrobinson, I don't think thickness is the key, as someone else pointed out (not here, can't remember where I read that), the iPod is thinner than the iPhone and it does include a headphone jack so that's clearly not the only thing keeping the iPhone thicker.
Also, as your survey implies, I think a LOT of people (possibly not in the 'audiophile' community) are going towards wireless headphones, they're just so much more convenient.
To me, this is a bit like when apple dropped the 30 pin connector on the iPods/iPhones (or floppy disks on the iMac), it's going to be annoying for a year (while people transition, have to buy new cables, have to get adapters, etc…) and then everyone will get over it because it'll be better.
Alex.