Specifically on February 25th in North America and February 28th in PAL countries.
New (prerendered) trailer!
I am, I'll be honest, a bit worried about Thief. Those who went hands-on with the game at E3 were only tepidly positive about it - it sounds like it's a bit janky, and, at the very least, needed a lot of optimization. I worry that, perhaps, Dishonored has gone and overtaken the franchise that inspired it.