First of all, nothing will dethrone WoW any time soon, and that's because WoW is a cultural phenomenon, a game that was at the right place at the right time. It was backed by a venerable and popular gaming franchise, it was done by (then) one of the best dev studios out there, it did a great job a streamlining the normally unwelcoming MMORPG genre and it came around just as a broader audience was starting to get curious about this whole MMO thing. This gave it the initial momentum that allowed it to snowball (wanna try one of those MMO things? why not WoW? everyone else is playing it). It was a perfect storm of events and it's highly unlikely it'll happen again in te near future.
That being said, I don't give 2 shits about Titan. No real details were released, nothing concrete was known about the game, I can't really feel bad for it being canned when for all I know it was a Douche Enema Simulator. What am fairly sure is that it siphoned resources and team members away from WoW and the game suffered as a result. The decline in quality seen with Cataclysm and Mists, as well as the insultingly long drought of content at the ass end of Mists are likely consequences of that. Now they are rushing to get Warlords out ASAP, and that will likely result in cut corners (well, it already has) which will undermine what seems to be the most promising WoW expansion since Wrath.
All in all, I'm not sad to see Titan go, and I hope that this allows Blizz to free up resources to revive WoW, as well as devote more to its other projects. I find it telling that the most popular thing Blizz has put out in recent years is a newbie-friendly CCG that started as a joke sideproject...