"We're working on the sequel right now, to the prequel, and so the excitement is - I'm not gonna tell you, but - are they gonna talk or not? Part of the challenge was how to get across what was happening between the apes without words. In the end I think it was a good challenge for us. It created better storytelling."
This makes on tend to believe that the apes will indeed speak at some point of this film. It will be interesting to see the transition from their current communication skills to using words.