Men in Black 3 didn't perform as well at the US box office as the previous two movies, but it earned $445 million internationally. A worldwide take of $624 million is easily good enough to merit exploring sequel possibilities, and Sony has hired a writer to work on the new story. According to The Hollywood Reporter, Oren Uziel will be creating a Men in Black 4 draft for Sony.
This isn't anything Sony is rushing into, though. Uziel has also been hired by Sony to work on a draft for a 21 Jump Street sequel, which takes priority with the movie already having a release date of June 6, 2014. There's no word on what Will Smith's involvement will be, but it will likely depend on the final script.
Previously, Oren Uziel worked on The Kitchen Sink, a project at Sony where vampires, humans, and zombies team up to save their town from an alien invasion. He was also involved in the latest attempt to get Mortal Kombat back on the big screen.