The Jump Festa trade show has just released the new Pokemon crossover game: Pokemon + Nobunaga’s Ambition. It is a DS game that is to be released on the Nintendo DS system in Spring 2012 as a collaborative work between The Pokemon Company and Koei, the makers of Nobunaga's Ambition.
Nobunaga's Ambition is a turn-based strategy role-playing game which was released in Japan.
It appears that the game takes place in the ancient past with Pokemon Trainers, both the female and male players will start out with an Eevee. There are also military soldiers, Oichi with her Jigglypuff, Mitsuhide and his Articuno, Shingen and Groudon, and Kenshin with Mewtwo as well as Nobunaga with Zekrom.