According to The Verge multiple sources familiar with Microsoft's Xbox plans have revealed to them that Microsoft will introduce a feature that allows the console to take over a TV and set-tip box in a way that is similar to Google TV. They understand that the next-generation Xbox will require an online connection to use the services, allowing them to be always-on for streaming and access to television signals. Apparently it will work by taking a cable box signal through an Xbox via HDMI, which then allows the console to overlay a UI + features on top of the existing set-top box.
The sources also say extended support for various cable services will roll out over time, but basic functionality will be available at launch. An event detailing the console is expected to take place in May.
Source: The Verge