http://variety.com/2017/film/news/be...ct-1201971566/
“There are certain characters who hold a special place in the hearts of millions. Performing this role demands focus, passion and the very best performance I can give. It has become clear that I cannot do both jobs to the level they require. Together with the studio, I have decided to find a partner in a director who will collaborate with me on this massive film. I am still in this, and we are making it, but we are currently looking for a director. I remain extremely committed to this project, and look forward to bringing this to life for fans around the world.”
He's staying on as a producer and obviously the lead, and looking for a new director; according to the article, Matt Reeves (War of the Planet of the Apes) is on the short list to replace him.