Wired headphones are great for a bunch of reasons. They're inexpensive. If one comes loose you won't lose it, as the cord will catch it. They don't require being charged. They'll last as long as you take care of them. You can share a headphone jack with a simple splitter (great for kids on the plane). You can use a headphone jack to interconnect with literally billions of existing audio devices.
Wireless ones require the added effort of making sure they're charged. Drop one and it's gone. You have to keep it in your hand if you want to remove one temporarily. They're pricey. They require being paired and UNPAIRED if you want to use them on more than one device. And, no doubt, Apple's scheme will require only their proprietary schemes to work.
As for space savings, this is a problem Apple created for themselves. Honestly, I think most folks would rather have a more durable device built inside of a factory case. Better battery life is certainly possible if they'd actually make the phone that's already the size of the inevitable case that'll get put on it.
The question is whether the market leader, Samsung, will avoid taking the bait and doing something likewise selfish.