Can you play 4k content from USB on a 4k TV?

Morning all,

My mates asked me to get him a 4k TV in the Jan sales. But he needs to be able to play content from USB. I've looked at a few TV spec's and they all appear to have USB 2? I wasn't sure if that was fast enough to play 4k content?
Or is a matter of getting a media box that has USB and play that through HDMI?

Thanks