According to Xbox Wire, the Xbox One will require you to connect to the internet at least once every 24 hours. If you don't, you won't be able to play your games offline. This isn't just games that will use the cloud, this will be every game. Microsoft did assure us however that you will still be able to watch TV and movies on your system, just not games. You can check out the system's networking requirements below.
Networking Requirements:
To ensure Xbox One works optimally and can offer the experiences described above, it is designed with the following networking requirements:
- For an optimal experience, we recommend a broadband connection of 1.5Mbps. (For reference, the average global internet connection speed as measured recently by Akamai was 2.9 Mbps). In areas where an Ethernet connection is not available, you can connect using mobile broadband.
- While a persistent connection is not required, Xbox One is designed to verify if system, application or game updates are needed and to see if you have acquired new games, or resold, traded in, or given your game to a friend. Games that are designed to take advantage of the cloud may require a connection.