Wow, that's very sad news. Titan Quest and Immortal Throne were absolutely wonderful games. Having just finished IT, I enjoyed TQ+IT even more than Diablo 2.
Assuming the sales were not what we would have expected - I wonder if WOW has made it harder for this sort of game to be successful. I find it hard to imagine a better Diablo clone than TQ, and if TQ can't move enough units to be a hit, I wonder what could?