Per an NFL press release:
The Week 16 Minnesota Vikings-Philadelphia Eagles game on Sunday, December 26 will be played at 8:20 PM ET on NBC and the San Diego Chargers-Cincinnati Bengals game that day will move to 4:05 PM ET on CBS, the NFL announced today. In addition, the Seattle Seahawks-Tampa Bay Buccaneers game will move from 1:00 PM ET to 4:15 PM ET on FOX
NFL knows its ratings makers and Michael Vick has been that guy this season (ratings for Eagles/Cowboys game last night were the highest for SNF this season). The Eagles are currently battling for the NFC East title and the Vikings still have an outside shot of making the playoffs, as well. Overall, this is a good decision by the NFL, although some might bicker about seeing the Eagles for a third time in the final six weeks of Sunday Night Football.