You'll never need an adapter if you never buy an audio-producing device lacking a jack.
Passive attenuation seems to be almost as good as active in my experience. And when you factor in that the headphones no longer need a battery, it's a net benefit in my book.
Most people aren't upgrading their phone for audio functionality (I believe cameras are the biggest driver of upgrades). The fact that you need an adapter to continue using your favorite headphones isn't going to raise many eyebrows among the general public, especially when they are mostly moving to wireless headphones anyway.
Passive attenuation seems to be almost as good as active in my experience. And when you factor in that the headphones no longer need a battery, it's a net benefit in my book.