While it's a bit much to say anything definitive about domain registering activity, it does raise an eyebrow. We know that there is a large team, filled with some amazing people, working hard on Titan. Could Project Blackstone be Titan? Speculation is interesting here; although we really have no idea.
What we do know is that we'll be keeping a close eye out on these domains, and you should too... Something might pop up suddenly one day that we all will want to know a whole lot more about.
We've reached out to Blizzard to see if they have any comment on these domains, but we're not expecting anything noteworthy.