Or, "Ecology: You're Doing It Wrong."
The movie After Earth features Will Smith and his son on Earth...millennia after humanity has left it. My immediate worry was that this new Earth would be like the book Fragment. Earth has probably evolved into a whole planet of super-preds, each one deadlier than the last. Most likely, they will all exhibit "Hollywood Predator Syndrome," making them have moves that no real predator would have, like relentless pursuit of prey. (Ambush tactics are more effective on humans for a number of reasons.) Good idea, but will probably be flushed down the toilet.
The problem? Unless the ecology has become so cutthroat that everything is as intelligent as a human being, it does not have any reason to be as lethal to humans as the trailer proposes. Humans have been gone for quite a long time. In theory, we can demolish everything because it can't take us after lack of exposure. We've wrecked nature; we can do it again.
Let me put it this way: Humans are nature's nightmare. Intelligence solves most of the issues that keep other apex predators limited. We can eat anything. We have no reproductive season, allowing for a reproductive rate on par with rodents. Where humans go, environmental destruction follows. Let's not even get into the flora and fauna we absolutely must have everywhere.
Does this mean that a species could not possibly adapt to humans enough to be a formidable predator? No, not at all. Humans have some exploitable weaknesses.
For starters, we are really visual animals, enough so that hearing and smell have suffered in favor of things like color vision. We depend a ton on sight for things like body language, too. Unfortunately, we are still not as visual as eagles, leaving humanity with a very odd sensory spread. Sufficient camouflage or light diffusion would already give a predator a serious edge. Throw in a better reproductive cycle than most preds and you have something that could likely trim the human population down. Let me restate that: not demolish, but trim it down, eliminating the weak and sick like predators are supposed to do.
Another tip for anyone trying something like this: small things matter. It's easier to kill one large predator than it is to stomp out a lot of small ones. Humans are good at strength in numbers; some researchers think we learned this from wolves. When the numbers are even, the fight is suddenly a lot more terrifying. It's even more threatening when humans are outnumbered. Cloverfield actually did this aspect really well; the parasites on Clover were small, yet vicious, and perhaps even more threatening than the giant monster in New York City. The raptors in Jurassic Park were another stunning example of big not always being better. This trailer uses baboons of some sort; IMO, not a smart move.
Also, for a post-human scenario to work, something had to evolve to cripple technology. Sensing electromagnetic waves on land might actually help species survive; you can avoid/detect humans easily now that everybody's carrying a Blackberry or iPhone. Just out of spite, someone should sic electricity-sensing rodents on Facebook HQ and see what happens. I doubt After Earth will consider this, though.
Once I looked it up? Oh, wow. This looks to be as bad as The Room if the sheer amount of personal investment Will Smith put into it and Shaymalan as director are any indication. Nice try, Hollywood. I'll wait for Rotten Tomatoes to deliver you justice.