Dishonored was just announced by Bethesda Softworks as being in development by Arkane Studios. Arkane was acquired by ZeniMax in late 2010 and has previously worked on Arx Fatalis, BioShock 2, and Dark Messiah of Might and Magic.
Nothing is really known about the title just yet outside of the fact that it will be a new first-person action game. It is slated for release on the Xbox 360, PlayStation 3, and Games for Windows (PC) in 2012.
Game Informer is going to have a month full of details when August rolls around. Subscribers will get their issue early in July. In addition, keep an eye on the official Dishonored website for fresh information.