I've often wondered what would happen if there was a true discovery of a lost book of the Bible. Rather than something revelatory that would devastate the foundations of the Church it would probably be a modest work that would simply enhance what is already in the Bible.
Last year when The Da Vinci Code movie came out there were a lot of stories about the “Gospel of Judas” and other so called "lost" books of the Bible. Although the media portrays these as sensational events, biblical scholars know that these are not books that were lost, but were widely known about during the time the Bible was canonized. These writings were rejected because they didn’t conform to the true message of Christ. They weren't lost or forgotten about -- they were thrown away.
Even in their own lifetime the original disciples of Jesus had to spend energy combatting heresies that were creeping into the Church. In particular, much of the Apostle John’s writing was in response to the growing problem created by gnostic beliefs disguised as Christianity.
But what if there was a newly discovered work that could conclusively be proven to have been written by an Apostle, such as Paul? If it matched his writing style, and if the work didn't offer any new revelations (or blasphemies) but merely supplemented his other writings, what would be the response of the Church?
Would we accept it into the canon of Scripture or would it forever be a curiosity, a humble footnote. Perhaps we would accept it, believing that "in the fulness of time" God had revealed more of his Word.
Either way, I'm sure that some publishers would be quick to market a "Bible 2.0".