What is the cost to upgrade my X1 DVR to 4K?

I have a Sony Bravia Television that can output 4K video if provided, however, the only 4K I am able to receive is from internet broadcasts. I have been receiving commercials from Comcast regarding the Winter Olympics in 4K, but my X1 DVR cable box is not capable of transmitting those broadcast signals. How can I rectify this situation?