According to Michael McCarthy of USA Today, the NFL will plan to refund fans the price of general admission tickets of all games cancelled in 2011 due to a work stoppage, preseason and regular season. The guarantee however does not apply to club seats, luxury seats, or personal seat licenses (PCL's).
"We are working hard to secure an agreement with the union that is fair and forward-thinking to ensure our game is sound and strong well into the future," NFL Commissioner Roger Goodell said in a statement. "We know we will reach an agreement at some point. We all want football without interruption, but our fans are entitled to know now that they would receive refunds if any games are canceled," Goodell added.
The article does not however mention what would happen if the league decided to use replacement (UFL anyone?) players or "scabs" to contiue play.