Conan O'Brien's final Tonight Show on NBC Friday night did the unthinkable.  It garnered prime-time size ratings, getting a 7.0 share on a night when television viewership is notoriously low.  Conan's previous high rating was a 3.8, when he premiered on the show last June.  Jay Leno's "final" Tonight Show got a 3.4 last May, which translated into approximately 12 million viewers.  Expect Conan's final viewer numbers to come in around 20 million, if not more.