Hideo Kojima is in Dubai at the moment, for a press event. IGN Middle East published an interview, that can be found here, or summarized below.
Kojima never thought the Metal Gear series would go on for 25 years, but it happened before he knew it. He also emphasized that while Metal Gear Rising is a spin-off that is meant to appeal to new players, Ground Zeroes will be conventional.
For Rising, the Kojima Productions staff insisted on using Raiden as a protagonist. Kojima himself would have chosen Gray Fox, but in that case he feels he would have to write the script and be very involved in the development of the game himself. Rising on the other hand could be worked on without him.
FOX Engine is designed to not only look better, but also have better functionality that allows new kinds of gaming experiences. Kojima couldn’t say much about that though. What he could say is that the engine is very efficient and with it, the studio is able to create games much faster.
When asked about the Phantom Pain trailer, Kojima laughed and said he liked the visual style and the lighting in it. Regarding the fact that the protagonist looks a lot like Snake, he said that it ‘might have been an inspiration’.
Kojima concluded by saying that Ground Zeroes will take ‘a little more time’, and people can play Rising in the meantime.