According to Adam Shefter, the NFL designed this year's schedule so that they could miss 3 weeks of the season and not lose any games. All the matchups in week 3 are between teams with the same bye week so they could move those games to the team's bye week. They would also skip the extra week off between the Championship games and the Super Bowl so the SB would only be moved back one week.
Also, none of the week 4 games are division games. Schefter said that there has never been a week in an NFL season without a single divisional game so that would obviously be done on purpose; if the lockout went further and the NFL had to cancel some games then they could lose week 4 and not miss any divisional games.
This might also explain why the Browns' schedule is so odd, that they play five divisional games in the last six games. The NFL wanted to have most of those games in the second half of the season so they wouldn't miss those games if any were cancelled because of an extended lockout.