Aaron Hernandez had advanced CTE

Be careful believing what is said by a plaintiff's attorney during a press conference. And how many 27-year-old brains have they tested for CFE to support the claim that it's one of the worst cases ever in a brain that age? Is it also one of the best results because it was, for example, second out of three?

This is the statement by Boston University's Medical Center on Hernandez.
www.bu.edu/cte/2017/09/21/bu-cte-center-statement-on-aaron-hernandez/

The BU brain bank has over 270 brains diagnosed with CTE The other big center for CTE research is University of Pittsburgh;. I don't know how many brains they have.
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This study, five years old, indicates that several of the brains with CTE were younger than Hernandez.
concussionfoundation.org/about/press-releases/press-release-sample-one

Boston University receives substantial money from the VA to do these studies.

If you're having problems with impulse control, shouldn't you kill people in the night club instead of waiting until later

Why isn't his despicable fiance suing UFlorida and Bristol High School?

I would think they'd also need to prove the CTE was the principle cause of the suicide 

The link below is to an article about a University of Pennsylvania lineman, a team captain, who committed suicide seven years ago. His parents sent his brain to Boston University and a pathological examination revealed early stage CTE. Boston University physicians cautioned that it would be a leap to say that CTE was the sole cause of his suicide.

The player never had a concussion, never complained of a headache. But a telltale clue can be found in how he played football as a youth, starting at age 9. As his parents said, he loved hitting, and the physical contact from the start.
www.nytimes.com/2010/09/14/sports/14football.html

Five years earlier, another Penn football player committed suicide, mid-season. I can't find a reference to his brain ever being autopsied. But this narrative of his behavior indicates the player became deeply troubled.
www.espn.com/espn/eticket/story?page=ambrogi
Follow-up
www.espn.com/espn/eticket/story?page=ambrogi&num=2

If Ambrogi had committed suicide five years later, quite likely, based on what is now known about CTE, his brain would have been autopsied. And I suspect the lineman's brain was sent to BU because of Ambrogi.

The Ivy League is ending full contact during practice, no tackling.
www.nytimes.com/2016/03/02/sports/ncaafootball/ivy-league-moves-to-eliminate-tackling-at-practices.html
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Yes, the Patriots and the NFL are being sued as they have the deeper pockets. I don't know whether the case will ever get to the point where a BU doctor will be asked whether, given the severity of his CTE, Hernandez had CTE while playing at Univ of Florida.

BU researchers have discovered a biomarker that could potentially allow for diagnosis of CTE in living brains: deadspin.com/bu-identifies-biomarker-that-could-allow-the-living-to-1818840010

If it does turn out to be a reliable diagnosis tool, then my best-guess answer to your question is yes. 

You already have the horror stories of players like Junior Seau and Rashaan Salaam committing suicide, guys like Chris Borland and John Urschel retiring young, retired players like Cris Carter saying that they're terrified of what might happen to them in the years to come. I've spoken to friends who played in high school and college that are concerned that they might have CTE. I haven't seen hard figures, but I have to believe that the number of parents who are willing to let their kids play football has to be plummeting (I don't have children, but I know that if I ever do, I'll do everything in my power to keep them away from the sport).

The correlation already exists, but the hard evidence is still missing. This could be it.        

Boxing still exists. It may be the canary in the football coal mine. The canary is breathing well now

What I was trying to convey was that if boxing has not been banned, after calls for its demise for 100+ years, then football--safer and exponentially more popular--will not be banned for safety considerations in my opinion.

Jake LaMotta just died at 95. of pneumonia. He appeared in an off-Broadway revue five years ago, which suggests he had had most/all of his mental faculties at that time. .

For every LaMotta, there is a Mohammed Ali.

I would consider boxers to be self-employed, so the calculus of risk for an employer (e.g., NFL team) doesn't enter into it. In the NFL, one is compensated (rewarded) for being on the field. as the employer's compensation for a benchwarmer is a lot less. The employer is incentivizing contact, often violent contact.

Boxing isn't banned, but it's popularity is far below peak levels. And participation is much lower than football, as you note.... but that means its less of a public health concern.

In short, boxing is essentially dying on its own.