The purpose of the salary cap is to limit the total amount of money spent on players and maximize the profits for the owners. Anyone who does not understand this should never have passed a college level course called microeconomics. (usually called Econ 102) The owners didn't insist on the CAp to make the league more competitive, they did it to make more profitable.
The only way that the salary cap goes away is of the NFLPA decertifies as a union and wins an anti-trust case against the NFL. The owners will fight to the death to keep the salary cap, if they had to (they don't) they'd give up the draft before they'd give up the salary cap. This would require the players enduring a multi-year lockout and hoping that the Supreme Court eventually decides in their favor. There's no chance of that happening with the current court and even if there were it wouldn't make any sense for the current players to give up 2-3 years of their career earnings in order to benefit future players. That's why the NFLPA has always lost for the last 50 years.
Everyone is complaining about high QB salaries but I think you're wrong. Considering the way the game is played now there's no doubt that a top 10 QB is worth far more than a top 10 pass rusher or OL. Easily 3 times as much but they don't get paid that much more. The thing is if you have a top 1 or 2 QB it makes a big difference, but an 8-10 QB, hasn't been worth 1/2 of Brady. However if the rest of the team is good/lucky enough and the above average QB has a hot streak in January-February you have a shot at lifting the trophy. Maybe you even have that chance if you have a marginal starter but it's a much smaller chance.
Teams will overpay for slightly above QBs because guys like Brady, Rodgers, Brees just don't become available unless they get old or are serious injury concerns. The above average guys at least give you the hope of victory and it's not that hard for teams to sell the vast majority of their fanbase on a "good" Qb being about to develop into a great QB.