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Back in March of 2011, Gonzalez left Obsidian Entertainment and joined Warner Bros. Games where he worked as lead designer for Middle-earth: Shadow of Mordor, a yet-to-be-released RPG prequel to The Lord of the Rings. According to his LinkedIn profile, Gonzalez left WB Games back in August of this year and had joined Guerrilla a month later.
As for what Gonzalez is developing with Guerrilla, he's written that he's, "Up to something new. Couldn't be more excited."
Oooh! Let's guess stuff!
Fallout: New Vegas writer joins Guerrilla Games [GamesIndustry]