A new subcategory of the Diablo III website was added very early this morning, titled Reaper of Souls. The above image is all the site holds for now, and if you're unable to read the writing it is ostensibly a quote from the Book of Tyrael, saying "Death, at last, shall spread its wings over all".
Now, while this is by no means a complete, firm confirmation that Reaper of Souls is the title of the next expansion, it's certainly looking that way. So that leaves the question of The Dark Below -- what could it be, if it is even a trademark? It did show up eventually on the US trademark registration site, but it's certainly not conclusive. So that adds to the recently registered "Cute But Deadly" trademark in the list of marks of mystery. What's your take?