In addition to what was made public by the Warren Commission , the House Assassinations Committee, and other means, the JFK Assassination Records Collection Act of 1992 resulted in the release of about five million pages of documents. They are available for review at the National Archives and Records Administration in Maryland and have been mined by researchers, with key documents posted online.
An administrative review board though agreed to withhold about 1,100 records, each comprising from 1 to 20 pages. These records -- tens of thousands of pages -- are considered to contain information about confidential sources or methods or to have national security implications.
The Act further requires that all records have to be released by 2017 -- unless the agencies involved petition for them to remain classified. My guess is that some will be released and some withheld, with ongoing Freedom of Information Act litigation perhaps causing the release of more documents at irregular intervals.
One set of documents in litigation now is the service record of CIA officer George Joanides. In 1963, he was the CIA's liaison with an anti-Castro Cuban exile group known as DRE, which the Agency was supporting with payments of $50,000 a month.
Although formally based in the CIA's JMWAVE office in Miami, in 1963, Joannides was living in New Orleans, which had a spurt of anti-Castro activity by the DRE. Part of that included a street confrontation with Oswald and a prior effort by him to join the organization.
Notably, years later, Joannides turned up as the CIA's liaison with the House Assassinations Committee -- and falsely denying that the CIA had anything to do with DRE or Oswald. Joannides is now dead, but George Blakely, the House Committee's former staff director, regards the deception by Joannides and the CIA as so significant that he called for the assassination investigation to be reopened.
I think that Oswald was a sincere defector to the USSR and not a CIA plant because he had genuinely pro-Communist views and was too psychologically unstable -- and plain stupid -- to be a reliable agent. The more likely scenario is that the CIA contacted and sought to debrief Oswald after his return, perhaps requesting that he would let them know of any overtures from the Soviets or Cubans or even paying him a stipend.
In any event, although Oswald was on the CIA's radar, by the summer of 1963, he seems to have wanted to go back to the USSR or to go to Cuba, and that may have provided the motive for him to shoot Kennedy as proof of his communist bona fides. Maybe Oswald was also manipulated and used in a larger assassination conspiracy organized around him. Or perhaps he was a patsy who never even fired at Kennedy.
I think that a definitive resolution is possible -- although we may not live long enough to see it.