According to SlashFilm, Spaniard Juan Carlos Fresnadillo will replace Gore Verbinski in the director's chair (though Verbinski will remain as a "producer"). Never heard of Fresnadillo? He's the guy who directed 28 Weeks Later, and...nothing else you've ever heard of.
Whether you liked his zombie sequel or not (brilliant opening aside, I hated it), replacing Verbinski with a relative unknown is certainly a step down for the production, which was—courtesy of the big-name director and big-time budget—at one time being hailed in this post-Peter-Jackson-Halo world as Hollywood's first crack at really taking a game adaptation seriously.
Juan Carlos Fresnadillo To Direct Bioshock [SlashFilm]