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David Letterman is planning on retiring next year.  He's put in a great run....He explained that he's done over 5,000 shows, around 4,000 for CBS and 1800 on NBC.  He has been hosting the late show since he was 34 years he'll be 67 on April 12th. I'm taking a poll: Who could possible replace the one, the only David Letterman.  Who is your pick?