I would be sadly disappointed to see Apple peddling this kind of snake oil. Phil Schiller may well get up on stage and use words like "hi-res audio" to justify dumping the headphone jack, but here's the reality of it:
1) "Hi-res" audio is indistinguishable to humans from traditional red-book CD, 44/16 (dithered) FLAC: https://xiph.org/~xiphmont/demo/neil-young.html
2) You're going to have to buy new wireless or lightning-enabled Beats headphones, or you're going to have to buy an adapter.
3) Beats headphones are garbage, by any measure you care to choose. And ridiculously overpriced.
4) Bluetooth headphones are always a compromise with sound quality, and this new iPhone (like all previous iPhones) is likely to support only A2DP, since aptX requires 3rd party licensing - something Apple simply doesn't do. (A new, Apple-proprietary, Bluetooth format is a possibility - something that would only work with Beats wireless headphones. That would certainly fit within Apple's current modus operandi.)
5) Lightning-equipped headphones and those lightning-to-3.5mm dongles/adapters are going to be quite expensive, because the lightning port (being purely digital) will mean each device (headphones or adapter) will require MFi licensing fees, a separate DAC and a separate amp, which makes no sense, given that the iPhone itself will still have an internal DAC and amp (to drive its internal speaker).
It would be an incredibly cynical move for Apple to ditch that 3.5 mm audio jack.
Very good points from the consumer-vantage point. You forget it makes good business sense for the Apple shareholder. This has been in the works ever since Apple bought Beats, to lock Apple customers in with fewer alternatives so Apple charges an exorbitant amount for proprietary headphones. Don't think Marketing won't kick in high gear with Apple "Pro HD" quality, provides "waterproofing" or other rubbish to justify it.
The day Apple bought Beats was hugely symbolic of the direction they are taking.