After the Joan Rivers fiasco in 1986, Johnny Carson sees fit to make clear with executives that David Letterman is his chosen successor and he won't settle for anything less. Leno is not yet the 'permanent guest host' he is today and Carson's wishes have already been made clear so come Carson's retirement in 1992, a peaceful transition is for the most part, ensured.
What becomes of The Tonight Show with David Letterman? Does he take the same comedic route he took on his own program OTL or a different one? What happens to Late Night? Do we see Leno take the reigns instead of Conan? How about the careers of Conan O'Brien and Jimmy Fallon? Does a true competitor emerge in the nineties? Etc. etc.
What becomes of The Tonight Show with David Letterman? Does he take the same comedic route he took on his own program OTL or a different one? What happens to Late Night? Do we see Leno take the reigns instead of Conan? How about the careers of Conan O'Brien and Jimmy Fallon? Does a true competitor emerge in the nineties? Etc. etc.