The makers of the film want to deliver the best quality of visual effects which will take time and that endeavour is the reason of the postponement.
Vijay Singh, CEO of Fox Star Studios says, "It was a unanimous decision to release the film on September 30, 2016. This would give the team some more time to present the film to the audiences in the best way. We, in no way wanted to compromise on the visual experience that director Neeraj Pandey is set to create with this movie."
(mid-day.com)