Everyone wants to be able to print and say that Bolt is the greatest sprinter ever, so if he loses, people will still just say, "Well, despite this, looking back on his career, he's still the greatest."
When Mo loses, people will say it's poetic symmetry -- because it will be. Just like in 2011, he'll be run down by a young, no-name Ethiopian in the 10,000. I predict that 19-year-old Andalman (or however it's spelled) for the win. And people will say, "Well, I guess he (Mo) really was a 1,500 / 5,000 guy." And people will say, "I guess Mo was one of the greatest 5,000m runners ever, but it's now obvious that only Haile or Kenenisa can lay claim to being the greatest 10,000m runner ever."