The questions won't stop even if you maimed and torutred every member of the government who knew anything about the assassination. Even if they had solid, irrefutable proof that Lee Harvey Oswald was just a nutjob with a rifle who killed JFK, people would still speculate.
They made it 2039 to help ensure no members of the government who had classified information would still be in office when it was released. But it doesn't matter because the Pres. JFK Assassination Records Collection Act of 1992 says everything has to be released by 2017.
Even if they are released, there are way to many plausible theories to ever really gain traction. The mafia theory, the military theory, the oil industry theory, the LBJ Is An Asshole theory, the CIA Assassinates Everyone theory, the Lets Keep The Cold War Going theory, the Khrushchev theory, the crazy Illuminati theory, the Freemasons Are Fucking Crazy theory, the Sinatra theory, and the Israeli theory. Just to name a few. All plausible, none can be proven.
The only way to prove a crime would be if the government had covered up crime scene reports..which they did not, and only because they allowed traffic only minutes after the assassination, cleaned the car, and took JFK to Washington instead of a local coroner.
A lo hecho, pecho.