Polls like the one that Macrumors ran on this "question" are ridiculous. First, we don't know. We've seen the white complimentary ear buds, all kinds of other bluetooth and wired headphones, and there's one (1) set of headphones that uses this. The lightning port can take digital audio, hd sound, a custom coder/decoder, and it would be, as you might concede, something new and as yet unseen, so... There would likely be an adapter for legacy headphones. This kind of useless, biased towards the status quo surveys -- we all know what the current setup is, we haven't seen the iPhone 7 at all, so of course people react with fear of the unknown -- are the antithesis of Apple since the beginning, and certainly since Jobs' return. Remember all the moaning and groaning about the Lightning connector? And... how many people mourn the old huge, ugly dongle now?
Once you've got people accustomed to one way of doing things-- the ubiquitous audio connection, for instance -- and you hear a rumor that Apple might change it, we get a) an avalanche of negativity and b) since you now have people afraid of the unknown, you can say all the usual hate things about apple: they just want to sell adapters, it's all just to get it thinner, etc. But the usual way this thing goes is, if they do this, and you see they've used the extra space inside the case for new battery, or a better chip, and you get HD sound and a better DAC, and people will calm down. The Internet rumor mills are so broken.