Based on everything Apple has ever introduced, I'm expecting some new innovation nobody was anticipating.
Everyone here is assuming that Apple is going to get rid of the 3.5mm jack in order to push a proprietary solution when they don't have to, despite the competition, which makes absolutely no sense for a feature so arguably important.
They also assume that Apple is just going to offer the same level of current BT technology as a substitute. When has Apple ever just regurgitated the same solution as everybody else, at least without improving it somehow? They would be foolish to offer BT headphones that were identical to every pair already available with all the same short comings.
And if Apple does all of this as I'm expecting, significantly improving wireless audio as we know it, even if it's proprietary, then why would they offer an adapter in the box to discourage adoption of the new standards?
Assuming Apple really drops the 3.5mm jack in the iPhone 7, my money is on Apple re-thinking music delivery, and offering a wireless experience no one else can. Who cares if it's proprietary? Apple's entire ecosystem is proprietary. If it's better, it's worth it. For those who have greater needs, then there's Lightning, which is going to do far more than offer an alternate connection for headphones, so there's that. And ultimately, if I'm right and Apple is not doing anything the competition isn't going to be eventually forced to do to compete by removing the headphone jack, then Apple will have a head start over them by doing this now. Otherwise they're complete idiots.
I guess you don't know the history here. The Audio Industry is littered with many, many higher quality methods of delivery to re-monetise content. Let me recall a few... SACD, HDCD, 24-bit CD, ATRAC/MiniDisc, WMA/DRM (quality arguable), DVD-A, FLAC/ALAC.... All of these are formats that still haven't taken off. The *only* thing that has come close has been the adaptation of MPEG4 in audio... what you know as AAC. It is technically better than MP3 in about every way possible, and only caught on with 10+ years of iPod/iPhone support (it takes more processing power than mp3, by a little).
A few things...
"When has Apple ever just regurgitated the same solution as everybody else, at least without improving it somehow?"
Well, they're regurgitating the 3.5mm in the rMB. They didn't improve audio delivery in any meaningful way (not counting commerce) other than their ALAC/AAC support. Mind you that's a HUGE improvement, but it has very, very little to do with hardware.
Apple commonly includes low quality earbuds, and while their 2015 update is better, it's not something many are willing to pay for on its own.
"And if Apple does all of this as I'm expecting, significantly improving wireless audio as we know it, even if it's proprietary, then why would they offer an adapter in the box to discourage adoption of the new standards?"
If it's proprietary, then it can't be Bluetooth. That's an open standard. That would then take a large swath of their own products and make them useless. If Bluetooth is an option, but they have some "new" way of transmitting wireless audio, it would be the best kept secret in a very, very long time. Consider what you're saying... they are going to add an ENTIRELY NEW set of hardware in the phone - a different transmitter. That theory makes little sense because the point of getting rid of the plug is to save space. They would have a new low-power transmission process that has no product line, and no secondary device interoperability. Consider that for a moment... a publicly-untested solution that uses a new broadcast spectrum the FCC hasn't tipped, transmitting a different way? The only thing even possibly in that realm is to make the headphones connect via wi-fi, and that's just not practical in a hundred ways.
What you're saying could be "better" would require an adaptive device... an LDAC cable. That's probably the direction they're going, given the OEMs that are making Lightning headphones that have powered DACs in them. For all the other stuff, this is going to require a powered cable adapter. Luckily Lightning has that capability to power, but it's coming from the device in a much higher wattage than you currently have with the passive analog 3.5mm.
So even if Apple has a Third Way for getting audio from phone->speaker, it's hard to believe that it will be a net-positive. I'm not suggesting they won't, but removing the 3.5mm seems too early, and adding a technical challenge that will create a barrier to purchase.
As an investor, it's hard to see the benefit of removing a fully-compatible plug from a device that works with audio natively, from phone calls, to video and audio recording, microphones and accessories that use the plug, remote controls that use the plug as a trigger, music playback, credit card readers... hell, there's even a wind meter I've seen that goes in the 3.5. Removing that plug makes using ALL of those completely unavailable.
I would rather see every button on the phone removed before a plug gets removed. I could see them removing the Lightning adapter before the 3.5. It is literally the only i/o you can't reasonably replace. You can make the app button become 3d-touch on the back glass, you could take the volume buttons away, you can even make the power button a soft button. You can charge through contactless, and you can transfer data via wifi. You could even just go down to one super-button that is power/app/fingerprint. But any of those design choices... no matter what you do, you have to have a 3.5. Now, can you have an LDAC to do it? Sure. You can. It's going to mean a dongle for the rest of its days. It will mean the slow death of an accessory ecosystem that has been very important for its prosperity for a decade. It will confuse customers more than anticipated. All of this can be "gotten over" in a few years... but let's be clear about this. Samsung listened. They adapted their clone to be waterproof WITHOUT giving up the 3.5. They have a better camera. They have a better screen. They have almost everything better in hardware, with some exceptions. The massive problem for many with SG7 is Android. Worldwide, the SG7 is vastly more popular than iPhone, and iPhone is risking a lot by going away from what made it the difference-maker. It does lots of things easily.
If music becomes annoying on iPhone, as it is creeping towards now, iPhone 7 will be in serious trouble. Removing the 3.5 will accelerate those problems.
Edit, one more thing. If they really thought 3.5 was bad, why are they STILL including them on laptops and iPads?