Several sources have informed Kotaku that Eidos Montreal, the developer behind Deus Ex: Human Revolution and Thief, has cancelled an unannounced game they had planned to release.
Kotaku has contacted many sources and, finally, has found that this project may have been a game connected to the Japanese branch of Square Enix, the parent company of Eidos. It also seems that the project was a new IP.
Stay tuned.
Thanks, Kotaku.