Hideo Kojima sent out a tweet from his Japanese twitter account which contained an image, while the image is a mystery and shows a soldier crouching besides a tank he hinted that this is a game running on the FOX Engine. Could this be an upcoming game from Konami / Kojima? or a mobile / handheld sequel to a Metal Gear Solid game. Right now the only thing I can say is that the game looks like a stealth action game but other than that your guess is as good as mine on what the game could be. 
The image in question is below:
The only guess I have is that the game is a stealth based shooter or something similar, why else would the person in the picture be crouching in the blind spot of the tank? Had this been an action game like Rising it would have shown more slice and dice but the crouching character is proof enough that the game is stealth oriented, so the game can be ANY thing even a new project of Hideo Kojima and Konami.
Based on the graphics it looks like the game is more of a console game than a handheld considering the graphics on the tank and the background look so good, so the chances of this being a handheld game ARE possible but I am more inclined to consider this as a console game over anything else. For now all we can do is guess and hope for more information from the big man himself.
You can see the original tweet HERE or by clicking on the Source button below.
