The NFL salary cap has gradually risen since the lockout in 2011. The owners initially got the better of the deal between they and the players, but it was setup in a manner that would allow the players to eventually get a nice boost in the amount of salary cap each team would have to spend on them.
Bill Barnwell of Grantland did a nice breakdown of the increasing salary cap over the year, and where it figures to be in the years to come:
As you can see in the table below, the prescribed increases for 2014-16 restore the spending bumps to their former levels:
The NFL's increasing revenue stream, thanks to new TV deals like the one signed this offseason with CBS, will continue to cause a rise in cap space going forward.
This will benefit the Bengals, particularly in the next year as they look to sign A.J. Green, Vontaze Burfict, Andrew Whitworth and possibly Andy Dalton to long-term extensions.
Having an increased salary cap will eventually negate this advantage as players sign deals that pay them more and ultimately causes a rise in value for guys like Green, so getting him signed to a long-term deal now based on what other elite players at his position make is important.
The longer Cincinnati waits to re-sign him, the more his contract demands could skyrocket as his on-the-field performance increases along with an ever-increasing salary cap.