It is objectively impossible to justify the removal of the headphone jack for any reasons other than greed. An informal survey of Cracked employees revealed that ear bud wires have inconvenienced them approximately zero times (plus or minus an error margin of zero). In fact, they're convenient enough that companies have started selling wires for your wireless earbuds. In a lot of situations wires are better: Ever notice how every time you call tech support about a WiFi issue, they suggest running a cable instead? That's because, in terms of reliably transmitting a high-fidelity signal (the main thing wires do) they're still way, way better than any wireless tech. Not to mention that because they're shorter than the distance from a person's ears to the ground they act like a safety rope, letting your ears anchor your phone so even if it slips it doesn't reach the ground.
Apple has become to phones what Windows is to PCs: They know people can't switch without great time and expense, so they use that difficulty to squeeze their customers harder and harder. Yes, the sales will be similar to previous phones, but only because switching would be slightly more annoying than plugging in a dongle to your phone just so you can use a regular aux cable.