Removing the headphone jack from future MacBooks would be a mistake
I can understand the logic behind Apple's decision to remove the headphone jack from its latest iPhones. Some folks may not like it, but fact of the matter is that space is at a premium on such small devices. If a manufacturer can add meaningful features that improve the user experience by dropping the headphone jack then it is well worth it -- despite the fact that you can no longer charge your iPhone 7 or iPhone 7 Plus and use the headphones at the same time without buying a dongle.
But Apple is testing the waters to see if it could drop the headphone jack on other devices as well, as it is now asking users of the MacBook Pro with Retina display if they "ever use the headphone port". This is no longer about "courage". It would be change for change's sake.
The main argument for removing the headphone jack on an iPhone is that it takes quite a bit of space, which could be put to better use. And Apple has introduced some changes over the previous generation -- like a bigger battery, a home sensor with haptic feedback instead of a clicky button, extra speaker, optical image stabilization or dual-camera setup -- that are meaningful improvements that do not change the overall dimensions of the iPhone 7 and iPhone 7 Plus compared to the old generation.
However, MacBooks aren't iPhones. People expect to have a certain degree of flexibility on laptops as powerful as the MacBook Pro, and that means being able to plug different things in, like, you guessed it, speakers. The headphone jack on a MacBook Pro is not only useful for plugging in headphones but also full-fledged speakers.
You could replace wired headphones with wireless ones because MacBooks have Bluetooth, and you could even get used to the fact that they'll involve an extra expense (on top of what you'll pay for a new MacBook) and require charging. But if you have proper speakers, like I do, then you really do not want to find workarounds to keep using them.
Apple could throw an adaptor in the box or come up with some sort of dongle, but that would not really be all that necessary considering that MacBooks don't have to be that thin or space-challenged inside to go that far. Not to mention the fact that you do need a bit of thickness to make sure there is enough travel in the keyboard, and ensure that you can fit a large enough battery underneath.
Apple hasn't shied away from removing things that were deemed super popular and important in the past, but it did that to offer something better in return or because there was a better alternative available. For instance, I am sure that no one really mourns the loss of the built-in DVD player these days, as not a lot of people have to use DVDs anymore. You could be better served by a USB flash drive, no doubt.
But the headphone jack is still very relevant in the PC space primarily because there are lots of users who have purchased (pricey) speaker setups that require it to be there. Meanwhile, manufacturers haven't come up with a better alternative or felt the need to do so, because, like I said above, space isn't really an issue on devices like desktops, laptops or even tablets. And not to mention that the backlash would be huge.
Perhaps Apple could surprise us by revealing a MacBook design so good that users could forget about the lack of a headphone jack, but personally I doubt that it could happen. Quite likely, we'd be looking at a thinner profile and USB Type-C ports that few people could use without adaptors. And I wouldn't be surprised if there's also an adaptor in the accessory list, that would rob users of a port just so they could continue to enjoy their speakers.
Realistically speaking, desktop speakers aren't things that you want to replace. In the consumer space there is not much progress -- if any -- because all the improvements have long taken place. Manufacturers are adding small tweaks here and there to improve their audio offerings, but really, their offerings from today aren't all that different to those that shipped a decade ago.
Some folks that I know, like me, have speakers purchased in the last decade, that still work great today -- and they expect them to continue working for years to come. I assume that is the case with lots of MacBook users who use speakers while at the desk. Apple probably knows how many of them there are but, no matter, the number is unlikely to be small.
If Apple comes to the conclusion that it could get away with dropping the headphone jack then it'll probably be right. It is not the end of the world. People will continue buying MacBooks, but it would no doubt be a change for the worse, not the better.