Now that we've reached that deadline, the publishing is beginning, and his estate has split the pages into a trilogy, the first volume of which is coming soon.
Scholars are divided as to why Twain wanted the first-hand account of his life kept under wraps for so long. Some believe it was because he wanted to talk freely about issues such as religion and politics. Others argue that the time lag prevented him from having to worry about offending friends.
From the Upcoming ueue, submitted by nmiller.
I'd like to point out that just because the actual manuscripts are owned does not mean their copyright is. Even unpublished works pass into the public domain: in this case, 70 years after the author's death. So while any presentation or edits or whatnot may be copyrightable, the actual content itself still is not.