Response: The answer to your question is, "it depends." A federal district court recently released PARTS of the transcripts of the federal grand jury's inquiry into the Alger Hiss treason investigation, which occurred over fifty years ago. The court selectively released parts of the transcripts in response to a motion from a historical researcher, who was supported by various distinguished historical associations. The court did not, however, release all the transcripts, nor did it do so without going through a detailed analysis and finding that the release of the sections at issue was permissible.

All of which illustrates, as I've always said, that there's no half life for grand jury secrecy. That is, grand jury secrecy is presumptively eternal--it takes a lot to get past it. If someone wants access to these transcripts, they'll have to show particularized need for them (i.e., that they need specific, identified portions of the transcripts to avoid injustice in a pending judicial proceeding or, after the Alger Hiss case, apparently for valid scholarly inquiry), and convince a court of that. They'll also have to show that the reasons for secrecy (preventing flight of guilty parties, preventing tampering with grand jurors, encouraging witnesses to testify fully) are no longer compelling.