One day maybe someone like Apple will draw a line in the sand and do what we all know they do to nudge people towards wireless, but I don't see it coming for a long time if it ever does.
While I obviously disagree with your opinion, neither of us has any proof of why we think Apple is choosing to do what it is doing with the 1/8" audio port, much less the USB-C port on the rMB.
Which brings me back to the topic of this thread: "I wonder why Apple chose a headphone port instead of a 2nd USB".
As far as I know, no one has advocated for a wireless only solution as you seem to be asserting here. But the more ridiculous implication of your statement is that Apple will maintain the 1/8" audio jack forever, never "nudging" people to wireless, or worse yet allow someone else to do it.
However, the question is why would Apple limit the versatility of the rMB for a wider gamut of users, forcing them to expand their product line, and maintain and cannibalize two additional products like the MBA, which should have been EOLed, in order to keep a 100 year old technology like the analogue audio jack?
Here's what we do know -- Apple is promoting the rMB as a completely wireless device. They're promoting it as having a single versatile port because they've maximized every square mm of space. We know that the 1/8" audio jack was included, though overlooked when describing the Mac's single port, and; being one of the largest ports left, it barely fits within the slim profile of the case. We also know that late last year Apple opened up to third party developers the ability to create lightning audio interfaces, for headphones and the like. So from that alone, it appears that the 1/8" audio port is not going to be around on Apple products much longer, let alone never going away as you suggest. Just look at the attached pictures. Any slimmer and the port is gone on the iPhone 6, and iPad Air 2. The MacBook maybe has 1mm to work with and that's pushing it. Perhaps Apple will just declare they've made their products 'thin enough' in order to keep the 1/8" audio jack forever and fulfill your prediction.
At a minimum, I would expect to see Apple switch to a cheap set of Lightning earbuds for the iPhone 7, if not 6S. If they are going to give them away for free, why would Apple care if they are compatible with other non-Apple products. But they will need to work with the rest of the Apple products, all of which currently have lightning connectors except the Shuffle, and the Macs. The Mac's can all use lightning with a simple adapter. However, I have a sneaking suspicion that the Shuffle may just get a lightning connector, perhaps even bluetooth wireless, and just maybe lightning earbuds, along with more storage to justify the higher price. Whether or not it does in its impending refresh, in the end, getting rid of the 1/8" audio jack only allows Apple greater design flexibility as they continue to slim down their consumer devices to a single port, while making them as versatile as possible. If the rMB had a Lightning port instead of a 2nd USB-C, I'd still be just as happy since it would accomplish essentially the same thing -- a redundant versatile port. And if I needed to plug in an antiquated 1/8" audio accessory, I'd whip out my inexpensive, high quality, lightning to 1/8" dongle adapter.
Apple's design future is thin. The future of audio is digital. It's inevitable the 1/8" audio jack will eventually be history.