You do not have to go searching for another channel to get your Sunday NFL games. This is because the NFL has agreed to extend the contacts of both CBS and Fox until 2014.
What this means to you:
CBS will continue to be the AFC network until 2014 and will air Superbowl XLVII in New Orleans in 2013.
Fox will continue to be the NFC network until 2014 and will air Superbowl XLVIII in 2014.
On a related note, the NFL and Comcast came into an agreement for the cable company to air the NFL Network on it's second digital tier.