It's obviously significant that Karzai has not only agreed to a run-off, but has acquiesced to holding that run-off on November 7, rather than pushing it back until after the Afghan winter, as some thought he might try to do. And it does give the Obama administration some more room to operate. But how much? Just thinking in terms of timing, it's not likely we'll know the Afghan election results very soon after November 7; after all, we didn't get the final results of the August 20 election until just this week.
So if Obama really is determined to wait to see what the shape of the Afghan government is before deciding on McChrystal's request, we could be waiting a while longer.
What's more, Robert Gates--who's arguing, contra Rahm Emanuel, that Obama can't wait for the Afghan government situation to sort itself out before making a decision on military strategy--is right to point out that, even once the run-off results are in, we still won't likely know what we're dealing with in terms of the Afghan government:
“It is not going to be complicated one day and simple the next,” he said. “I believe the president will have to make his decisions in the context of that evolutionary process.”
In other words, this November 7 run-off news is good news considering the alternatives, but the situation is still very much a mess.