...they're just rumoured to be shipping the phone without one.
That's not removing. Nobody is having their existing phone amputated. The SE and 6S series will still ship after the release of the new phone, and they have headphone jacks. The existing, shipped devices have their headphone jacks.
If the new phone doesn't have a headphone jack, it'll be all over the Internet. There will be almost no way to avoid knowing that the iPhone 7 doesn't have a headphone jack.
Any "frustration" felt by users who then go and bye one, *knowing* that it doesn't have a headphone jack, *seeing* in the store that it doesn't have a headphone jack, having an Apple employing trying to up-sell them Bluetooth headphones after *telling* them it doesn't have a headphone jack... well, I have a suggestion for where they can plug their existing headphones.