But you could do that today if you wanted, but you have not done so. That should tell you something about whether there's an actual advantage to replacing the jack with a power consuming adapter, or if it's change for the sake of it.
There is no comparison to eliminating floppy disks which were already in steep decline because of better alternatives. The headphone jack is currently used by nearly 100% of all buyers who use wired headphones or earbuds.
What is this FUD about a power consuming adapter? The adapter doesn't have to consume one drop more power than the 3.5mm Jack does, and in most cases won't. But when it does, it will be to power things like noise cancellation, which currently requires a bulky battery in 3.5mm headphones, and more powerful amplifiers than Apple can include in the iPhone, to drive larger, higher quality 3.5mm headphones which can't be used effectively with iPhones currently. And Apple will control the amount of power that can be tapped for these purposes, likely requiring these headphones to have a slim built-in battery which can be recharged through the same Lightning connection, without additional chargers and cables.
And where are all of these affordable Lightning headphone options I could be using now? Are they easy to use? Does Apple fully support them? Does Apple offer a set of Lightning headphones to set the standard for third parties and provide the tools to make it a comperbale le experience to what a customer can expect from an otherwise wired 3.5mm headphone set?
Audiophiles do use Lightning outputs to get better audio from their iPhones. But they aren't fully supported by Apple, and tend to be kludgy affairs tolerated by those for whom premium audio is paramount to convenience. Commercial headphone makers go where demand is, and yes a few have built Lightning headphones for those audiophiles who want higher quality audio and convenience. They are prototypes more than anything -- expensive ones at that, like first gen Apple products that don't come into their own until the second generation after Apple has figured it all out. But the headphone makers have not embraced Lightning fully because there is no demand for it currently, especially for the average consumer, convenience trumps high quality sound, and for most, the cheap current 3.5mm technology is good enough, especially considering the commercially available alternatives.
All the paucity of Lightning headphones being used by the consumer currently tells me is that they aren't as affordable as 3.5mm technology, for use on hardware or audio that hasn't been optimized to justify the cost.
But your argument is specious at best. Using the floppy drive example you so casually dismissed, it's equivalent to telling someone who lost their floppy drive in 1998 that a USB thumb drive was a far better alternative to the floppy disk, despite the fact most customers weren't really using the Internet to transfer files, which was still slow and unreliable, even for a 1.4MB file. USB thumb drives were expensive, and good luck using it to transfer files to another user who didn't have one -- which was most everyone. It was far simpler, faster, and much cheaper, to to put a couple of documents on a floppy disk and walk them down the hall than any other solution available at the time. Of course USB thumb drives were a much better solution than the floppy, but for the office worker at the time it didn't seem that way. Imagine if the prevailing attitude had been -- 'hey you can add a USB port to your computer now and use it all you want, just leave our floppy drives alone' -- how long would it have taken to move people over to USB? Necessity is the mother of invention, and in this case the driver of adoption. Take away the cheap inexpensive thing that works as good as the new expensive thing, and people will embrace it. But it had truly turn out to be better, or people will cling to the old regardless of the inconvenience.
But ultimately this all misses the point, because Apple wouldn't be removing the headphone jack if they had a choice. To continue making the phone as small and light as possible while improving and adding features, something else has to go. And it's not just Apple, it's all mobile phone makers, because it would be suicide for Apple to drop something so widely used when their competition doesn't have to.
As to your last point, just what is the percentage of customers who chose to use the wired headphone jack on their iPhones? A recent survey of 1.000 Apple Store customers suggests it's not much at all, and as we all know Apple doesn't cater to niche markets.
