Busy day today, but you should check out Devin Rose's most recent blog post, in which he points out something that I'd never thought of. Protestantism typically views the prophetic age of the Old Covenant as ending long before Jesus, with a lengthy “intertestamental period” of about four hundred years. They claim that the ancient Jews closed the Old Testament canon around 400 B.C., and that there wasn't any new binding revelation until Christ.
But John the Baptist is an Old Covenant Prophet, and he's prophesying right up to the Baptism of Jesus. In other words, rather than a four hundred year dormition between the Old and New Covenants, there's a seamless hand-off. John the Baptist, the last (and greatest - Matthew 11:11) of the Old Covenant prophets, makes Messianic prophesies, and then sees them come true. You could add plenty of other folks, like Simeon (Luke 2:25-35) and Anna (Luke 2:36-38), on that list, too: Old Covenant prophets (and a prophetess) who saw their Messianic prophesies fulfilled in Christ.
But if all of that's true, if Old Covenant revelation doesn't end until after the birth of Jesus Christ, then the idea that we have to reject the Deuterocanon because the Old Covenant was already closed by 400 B.C. loses its credibility. The story of the Old Covenant, and its heralding of Jesus Christ wasn't over yet.