the issue with thinking the cap will go up $3+ million every year it that it absolutely will not. yes it will go up again next year by a good amount, but then the owners will opt out of the current CBA after the 2016-17 season.
the NBA players are notoriously bad at saving there money and get killed in every lockout, the odds of that changing are slim. so the 16-17 cap will be ~$68 million but the 17-18 cap (if there even is a season) will probably end up no more then $70 million and the 18-19 cap no more then $72 million.
its possible the owners will fudge the numbers some, plus with the Nets bleeding money the cap could go up only $3 million next year and stay the same for at least 1 season after the next lockout.