Would you really have a second USB-C port over just keeping the headphone jack?
Most people probably wouldn't really care for this, and the ones who do probably have portable media players already, so I would prefer to keep the headphone jack. The reality is, though, that USB-C appears to be the future.
Of course you'd still need two ports if you wanted to charge at the same time.
It would probably be more interesting to see smartphones that could use the headphone output as a digital signal, like a coaxial output. We want the 3.5mm output anyway, so why not just let it dump a digital signal to an external amp?
Mobile phones are thermally constrained these days anyway.