Currently the USB 3.0 ports are only for storage.
Samba and FTP is working, although we still have some issues with Samba when it comes to OS X and possibly also Linux and we're working on fixing these.
Future options that we're working on adding down the road and that we promised was print server and USB 3G/4G dongle support, but this is going to take some time to add.
Beyond that, we haven't really planned that much, but technically third party dongles for other wireless technologies would be possible.