I agree on the value of analog audio ports. But...
For a lot of intrinsically digital devices, adding an analog audio port is extra cost on both the electronics and physical side. So I'm thinking that *if* USB-C audio does take off, analog ports will become a premium feature and the very cheapest devices will be all-digital.
The biggest obstacle to USB-C audio won't be a lack of agreement on a standard or cost or consumer reluctance, though. The biggest problem is going to be Bluetooth, which has slowly been gaining traction and coming down in cost.
The biggest trend in gadget connectivity isn't digital cabling but rather wireless. WiFi. Bluetooth. Wireless HDMI. Wireless charging. NFC. Bluetooth is already so cheap to implement it comes for free on most WiFi chips. Bluetooth speakers are ubiquitous and cheap. Bluetooth headphones and remotes are increasingly common, increasingly cheap. So yes, adding audio out to USB-C will be trivial on the device side. But the real problem will be on the headphone side, getting the accessory makers to commit to a third line that will have to be priced cheaper than the Bluetooth line.
The time for wired digital audio may already be passed.
Analog audio will remain as a legacy port for a long long time just as the vintage analog AV ports still remain on TVs but eventually most portable electronics are going to go sealed and portless.
If anything, the longer term trend will be to all-WiFi connectivity (Internet of things) and possibly even power by WiFi for some very low power devices. We might see ereaders that trickle charge via WiFi or solar and WiFi. Indefinite battery life.
Still a ways off, though:
http://www.wired.com/2015/06/power-over-wi-fi/