I don't know about all that. The IAAF World Champs is still the #3 most watched sports event in the world and will be so with or without Bolt vs. Gay or Bolt vs. Blake or even (God forbid) Gatlin vs. Lemaitre.
But when you go to the main events outside the WC (and that's the real money for the race promoters) who sells tickets? You know the answer.
If Bolt loses to Gatlin, do you still sell 80,000 tickets in 75 minutes for an event 6 months in the future? They probably still sell out Zurich (for a rematch) and ISATF in Berlin, but what about Stockholm and Brussels?
Let's say they have a rematch in Zurich and Bolt loses that too. Now what about Rome, Paris, London next year?
The thing is (really big) stars sell (really big numbers of) tickets.
I suspect that the IOC wants the facade of complete testing and "clean sport" because that brings in the bucks from the US Corporations that bankroll the whole thing and they're doing it for "corporate image": I don't think druggies running fast is quite the image the CEOs of these companies have in mind.
But deep down, they want Bolt and they want Bolt to win. That's just the way it is with minor sports like track. It was that way with Carl, it was that way with Marion Jones in 2000, and was that way with Michael Phelps.