You have a point, but at the same time look at the next generation of players that are developing: Cam, RG3, Luck, Cruz, Gronk, Megatron, etc.
Maybe you're right and this is just the reign of offense but I dont see it ending for a while.
On the other side of the ball: Mark Barron, Chandler Jones, Von Miller, Patrick Peterson, Aldon Smith, J.J Watt, Bruce Irvin etc etc
Look at all the big-offensive names in the Lewis-era: Manning, Brady, Tomlinson, Moss, Gonzalez etc etc.
In general, for every x-offensive player there's gonna be that y-defensive player to counter that; not always equally but there'll always be an indirect counterpart. It's not really possible to go through a offensive-period like you say, shyt just wouldn't work in a game where balance is basically everything.