Jurassic Park 4 will be in 3D (apparently shot in the format, rather than post-converted). Casting has not yet begun for the film, so rumors of Bryce Dallas Howard, Sam Neill, etc. are not accurate (yet, anyway). The story breaks down like this:
JURASSIC PARK 4, set in present day Isla Nublar, is now an actual theme park, as originally intended by John Hammond in the first film. It garners 10 million visitors per year and is completely safe - until it's not. The park itself is described as very Sea World-esque and includes an area called the Isla Nublar Lagoon. That means underwater dino's for the first time. No indication of what kind, but there's concept art showing one of the aquatic dino's, as part of a show, jumping out of the lagoon and eating a strung up great white shark like it was a fish for a dolphin at sea world.
As part of a show, you ask? That's right, folks, this will feature "tamed" dino's. In fact, our source indicated that the usually menacing Velociraptors (which will finally be muzzled, along with the T-Rex - until they're not) will actually be used to help fight the threat, which begins in the form of a new dinosaur, not seen in any of the previous films (and not disclosed to us) shows to be much smarter than originally thought and is the main cause of havoc breaking out at the park.
So, to sum it all up, JURASSIC PARK 4 will take place back on Isla Nublar with a fully operational dinosaur theme park (I'm sure no expense was spared) that's both prosperous and safe, until a new dinosaur figures out a way to wreak havoc, causing the use of the now tamed Velociraptors (and T-Rex? Unclear) as a means to fighting the threat.
In fact, our source indicated that the usually menacing Velociraptors (which will finally be muzzled, along with the T-Rex - until they're not) will actually be used to help fight the threat
So basically the original Jurassic Park except with more dinos and lots more people. Which of course means lots more dino kills.