I personally can't wait for 1) OSes that can move seamlessly from phone UI to full desktop UI depending on the size of connected screens, and 2) hardware that can handle heavy dev work (multiple VMs, lots of random I/O) that fits in a smartphone form factor and power envelope.

Then sync would no longer be necessary because all you would ever need to use is that 1 unified device.

Until then, I use network shares on a cloud server through VPN for media, and Git and Vagrant/Docker for dev stuff.