It could lead to more revenue, but it could also mean that the fans may bore of the NFL sooner. It's hard to tell because if the season over-extends itself, it starts running into other sport's timeframes and television schedules. It probably wouldn't hurt the NFL too bad since it is the #1 or #2 sport in the U.S. right now.
And record books would have to be written along with the extra player injuries. Don't think it'd be worth it.