According to Japanese economy paper Nikkei Kojima has officially left Konami as of today, December 15th. At the moment he is starting a new company with former Kojima Productions members, and is in talks with Sony Computer Entertainment about his next game releasing on PlayStation hardware first.
Here is a translation of the article by user Zefah on NeoGAF:
Kojima Hideo, a famous video game creator known for the Metal Gear series has left Konami Digital Entertainment as of December 15th. He will form a new company where he will continue developing video games, with plans to release on platforms such as Sony Computer Entertainment (SCE)’s PlayStation.
He is forming the new company with people who worked under him at Konami. The rights to the Metal Gear series, for which he is most known, remain at Konami, so he will begin working on an all new title. Final negotiations with SCE are underway for this new game to debut on PlayStation.
Kojima is a world famous video game developer on the same level as Nintendo’s Shigeru Miyamoto, the creator of Mario. He is highly praised for his elaborate stories and use of movie techniques to create impressive visual imagery. Metal Gear Solid V was released this September and became a massive hit, selling over 5 million copies around the world.
Source: Nikkei, via lifelower Twitter, Polygon, JunkerHQ, NeoGAF