Robert Orci left the movie due to obligations for Star Trek 3: http://deadline.com/2014/09/power-rangers-roberto-orcis-star-trek-3-837131/
EXCLUSIVE: Roberto Orci has dropped out of Power Rangers because his Star Trek 3 directing obligation has created a scheduling conflict. He’ll no longer be exec producer of the film. It doesn’t change Lionsgate and Haim Saban’s intention to release the film worldwide on July 22, 2016. Ashley Miller and Zack Stentz will continue to write the script. Miller and Stentz have previously written the screenplays for X-Men: First Class, and Thor. Saban, who hatched the Power Rangers franchise, is producing with Brian Casentini, head of development and production for Saban Brands, and Allison Shearmur, who oversaw The Hunger Games when she was President of Production at Lionsgate. Erik Feig, Co-President of the Lionsgate Motion Picture Group, and Jim Miller, Lionsgate’s Executive Vice President of Production & Development, will oversee the project for the studio.
The film is a modern reinvention of the Mighty Morphin Power Rangers, a group of ordinary high school kids who find themselves infused with extraterrestrial powers and must harness those powers as a team to save the world.