In Apple’s mind I believe they see the iPad as a device in which you don’t ever need wires to use. If you do, you only need one at a time (either to charge while you sleep, or for headphones). Of course Apple’s preference is for you to use AirPods, but lacking that you can use the Lightning port.
I would bet then that the next round of iPad Air, and iPad mini models, you will see no headphone port.
The writing is on the wall for headphone jacks — eventually Apple won’t sell a single device that has one built-in. But this transitionary period will take a few years. I agree with Ben, I think the iPad Air and iPad mini are the next devices that will lose the headphone jack.
I think the iPad Pro will follow soon after, though. iOS devices represent a new era of computing and I think the “pro” iOS users are more willing to accept these types of changes. They’re the bleeding edge users who have already preordered their AirPods or plan on doing so soon. Apple will still probably hear some amount of backlash from them, but not to the same degree as they did with the iPhone — not even close.
I’m more curious about how long it will be before Apple ships a Mac without a headphone jack. And will that happen before they’ve been fully removed from the iOS lineup? Is this the type of feature that Apple will use as a temporary differentiator between the two lineups or will they transition both of them concurrently?