Just because they're removing the 3.5mm jack, doesn't mean it won't still output analog audio. They could very well push the analog audio over a couple of pins on the Lightning connector. The older 30-pin connectors did that. You would then use a simple Lightning to 3.5mm adapter.
If they don't do analog transport over the Lightning port, they'd be to just stick a DAC in the adapter.
Or they won't remove it from the phone at all. 99% of Apple rumors are wrong, so perhaps it's best not to spread FUD just yet. Also, Apple patents *a ton* of stuff. Of that, a small number makes it into production.
Either way, you'll still be able to use headphones, I guarantee that. It's sort of a basic requirement.