This Email was reportedly sent to Microsoft employees, which debunks the always online rumor
“Durango is designed to deliver the future of entertainment while engineered to be tolerant of today’s Internet. There are a number of scenarios that our users expect to work without an Internet connection, and those should ‘just work’ regardless of their current connection status. Those include, but are not limited to: playing a Blu-ray disc, watching live TV, and yes playing a single player game.”
Email leak comes from here