Speculation Question: How is the S5 going to work with Android Auto?

[ireknole]

I've been anxiously awaiting Android L and Android Auto to be released so I can start using my phone for media entertainment instead of an overpriced ipod touch. Since Samsung has disabled mass storage from their phones, my car (Hyundai Sonata 2013) cannot read my phone. From what I've read, android auto is a program that runs on the phone and is mirrored to your car (I'm assuming via usb). Since my car cannot read my phone, how is this going to work with Android Auto?