For a mobile device, 4G is more than fast enough for me.
What will the extra speed of 5G give me? I can watch HD content already. I don't use the phone for downloading much except an audible book once a month, and that tends to be when I am wifi anyway.
Okay, if I was to tether then maybe it would be nice, but at the speeds offered by 5G you could run a home network. Hell, even at 4G speeds you could run a home network.
I don't see any benefit to 5G speeds on a mobile device.