I think it is a very farfetched proposition that so-called "faithless electors" could have any effect on the final outcome. It has never happened before, and these days it is even less likely to happen. Electors nowadays are screened very rigorously so that only people extremely committed to their candidate are sent. Because of this, to become a faithless elector a person would have to essentially infiltrate a group of hardcore supporters months ahead of time on the guess that the election will be close enough that his or her defection will mean anything.
The idea that, on ideological grounds, electors who originally supported their candidate will switch to supporting the popular candidate is just not credible, especially in numbers great enough to affect the election.
However, if it DID happen, in those states whose electors are not legally obligated to stick to their candidate, it would briefly appear to be a done deal. By then every media outlet, every political office, etc., will have operated on the assumption that the other person won. It will be interesting to see if the meeting of the electoral college actually can change the built-up inertia of the assumption about who won.
I also believe in such a case there will be a legal challenge, which will go to the Supreme Court, which will find in favor of the Republicans no matter which side of the issue they are on. In other words, the SC will invalidate the faithless electors if that will help Bush, and it will uphold them, if THAT will help Bush. And I further predict that there will be four dissenting opinions.