The answer is yes. It's a well-known doctrine in law that if a case is moot and no longer applies, it could be used as a defence if they could show that there was a genuine change.
The charge would be that Iran has violated the genocide convention, however. So if in fact the incitement has not been in some way dealt with or punished in Iran, as it is supposed to be under the genocide convention--in other words, if Iran doesn't prosecute Ahmadinejad and the others--then you might still in fact have a case. But I think you're right that it would weaken the case. However, from what I've heard, especially from our other witness today, who is far more of an expert on Iranian politics than I am, it doesn't sound very likely that even the other candidates are going to bring about a massive change.