This doesn't exactly replace the set-top boxes currently used to access TV programming.
But M2 Research analyst Billy Pidgeon says it's likely a good option for families who want to able to access TV content in different rooms of the house, for example. With the Xbox, they won't need a second set-top box.
What they will still need is a subscription to Comcast or other pay-TV services. The Xbox may make it easier to access those HBO shows, but you'll still have to pay for them.