The tradition in the NFL nowadays is for the team that wins the Super Bowl to kick off the following season at home. The defending champions get to celebrate their victory one final time, and they get the Thursday night spotlight as the new season gets underway.
This year, thanks to a scheduling conflict, the tradition is being broken. The Baltimore Ravens won't get to open the 2013 season at home because the Baltimore Orioles have a game scheduled that same day. The league doesn't want to move the game up a day this year, so the Ravens are being forced to start the season on the road in the Thursday night time slot.
It seems like there has to be a better solution to this situation than having the Ravens go on the road to start the season, but since that's the plan, the Detroit Lions are now in the mix to host the defending champions. The Lions are one of the eight teams the Ravens will play on the road in 2013, and the NFL could theoretically decide to start the season in Detroit with the Lions headlining opening night. It's not likely, though.
Based strictly on ratings, a playoff rematch between the Ravens and Denver Broncos makes the most sense for the Thursday night opener. The Ravens also (obviously) have a road game against the Pittsburgh Steelers in 2013, and that would make a lot of sense as well from a ratings standpoint.
One thing potentially working in the Lions' favor, as pointed out by Pro Football Talk, is that the NFL may not want to give Baltimore such a tough matchup on the road to start the season. If that ends up being the case, the league could look for a lower-profile matchup that would still do well from a ratings standpoint. In that regard, the Lions make total sense given their star power (Calvin Johnson, Matthew Stafford, Reggie Bush, Ndamukong Suh, etc.).
Of course, it's important to consider that the Lions may not even be in the mix to host the Ravens in the season opener because of their Thanksgiving game. The NFL wants to get each team one Thursday game, and the Lions are locked into Thanksgiving. It's unlikely that the Lions would get two Thursday games in one season, so chances are the Ravens will open somewhere other than Detroit for that reason alone.
The 2013 NFL schedule, by the way, will reportedly be announced on April 16.