i think the film is rather brilliant, and that while projective science of the sort is tentative at best, it's at least an educated guess.

a more useful criticism, from my perspective, would be to point out that they don't talk about things like energy sources, or address the consequences of climate change. further, they treat america as though it exists on this world by itself. if america were to ever stagnate to such an absurd extreme, it would run out of energy before it ran out of food, and end up subsumed by the ocean in the process. further, some other culture would no doubt come in and wipe us out, as easy prey.

so, in that sense, this kind of future is unlikely, for the reason that we'd end up extinct before it happened.

but, in theory?

i have little criticism of the premise of the film, as it exists. it's not inevitable, surely. but, it's a reasonable projection of existing trends.

obviously, it won't be quite that bad 20 years from now.