I am looking forward to watching this documentary for entertainment purposes, but I don't expect it to affect people's opinions about religion much.
I have no doubt that both Krauss and Dawkins are very bright and insightful people. However, here is a piece of an interview I found somewhat naive:
Do you foresee a time when the conversation will be over?
LK: I think it’s frustrating. When I was a kid in the ’60s, I was sure that by now there would be no religion. In a way it’s very surprising that there are these momentary resurgences. I think it’s going to be a long road.
RD: If you look at the broad sweep of history, then clearly we’re on the winning side. I think things are moving in the right direction, probably not as fast as I would like to see.
Both of them seem to tacitly assume that religion ought to eventually yield to scientific progress and such. While this may be the overall trend in the West, or at least in the US, it has not necessarily been so elsewhere. I am somewhat surprised that the two rather bright guys seem to have these rose-colored glasses on.
The current and ex-Communist states are the most stark example. In the Soviet Union religion was marginalized for some 70 years, two generations grew up in the environment of state atheism, yet soon after the restrictions were relaxed, the Church has regained almost all of the lost ground. The situation was similar in the rest of the ex-Warsaw bloc (with less time under mandated atheism), and even in China, where the equilibrium was restored after the Cultural Revolution. The standard argument for this happening is "but Communism was basically a religion by another name", what with the various Cults of Personality and the beliefs in the One True Path.
This argument seems convincing on the surface, but consider a similar situation transplanted into a US setting. Suppose that, for whatever reason, after the Civil war religion was abolished all across the country together with slavery. Overtly religious activities are frowned upon and marginalized by the authorities. The community organizations like the Y, the Salvation Army, the Scouts and others do all the same work, only without mentioning God, or maybe replacing it with some secular symbol, like the Motherland/Fatherland/Abe Lincoln/Capitalism/Free Enterprise, whichever. The movie The Invention of Lying alluded to a similar setup.
Furthermore, imagine your parents and grandparents not attending any church, not taking you to the Sunday school to learn about Christ dying for your sins. They are still fervently patriotic and proud of the great achievements of your country, they wave the Flag and they are distrustful of the world outside it, but none of it has religious overtones. No one bothered to add "under God" to the Pledge of Allegiance. All the regular prejudices are still in place, like racism, homophobia (only without any religious references), misogyny etc. Sex education is in the same awful state. Again, this is how things were or still are in the former Eastern Bloc countries, so it's not much of a stretch. People still have their superstitions, like Friday 13, black cats, umbrellas and what not.
Science is respected, the Darwin's theory of evolution is accepted as much as the Newton's theory of gravitation and taught at school without any controversy. No Creationism. No one pays much attention to promoting atheism, because it's the obvious default position. No explicit training in Rationality beyond the usual lousy Critical Thinking courses. There are still churches, mosques, synagogues and temples, but they are mostly cultural objects, though some are active, enough to satisfy the needs of the tiny minority of believers.
A setup like that would be a dream come true for Dawkins and Co., wouldn't it? Then something bad happens. Say, the Great Depression all over again, or worse. The federal government loses all credibility and collapses, and the state governments follow suit (maybe there was some big conspiracy uncovered, or something). No social safety net, no Medicare, no jobs. Ordinary people barely scrape by to survive. What would you expect to happen religion-wise? Someone like Dawkins would probably anticipate a surge in observance, since "there are no atheists in foxholes", followed by a relaxation to the default state once things improve again, as they usually do.
Instead, what is likely to happen, if the experience of other countries is any indication, is the proliferation of religious beliefs and institutions, maybe institutionalizing of one dominant religion, as the leaders look for something to unite the people. And this elevated status of religion becomes the new status quo. It is not clear which way it goes from there, but there is certainly no guarantee that Atheism ought to win out, no more than there is a guarantee that Free Enterprise wins out, or that the Dictatorship of the Proletariat is the future.
This view might be overly pessimistic, if you are an atheist, and there might be some historical examples to the contrary, but I am certainly not convinced that religion will eventually fade away.