Diablo 3 is their a reason?

Now with StarCraft two coming out, and Warcraft fans having their day in the sun for the last few years. We are left with the question when is it Diablos time? Granted it took StarCraft ten years and the last Diablo game came out in 2001. I think it is a valid question but I ask you what is left to do in that world? *Spoilers ahead*

The reason I ask this simple question is in the first Diablo you do not have the power to kill Diablo and are forced to imprisoned him in a soul stone and hold him in your head, as you slowly go insane. Though since you only killed Diablo in the first one you still had two brothers left. In the second one you killed Diablo again well because you are a new hero and had to kill the old hero that had become Diablos host body. Then you got to kill one of Diablos brothers Mephisto. So once you had beaten the game you knew one brother remained, Baal.

Then the expansion came out Lord of Destruction. This allowed you to head into the frozen north of the Barbarians homeland. Though this expansion you were able to go toe to claw against Baal the last of the three brothers. So once he was vanquished your long quest had come to an end. Well no matter what happens the world stone is destroyed and you are left with a uncertainty of what will happen in the world.

Though even with this uncertainty you have still killed all of the prime evils. So the job has been done. So what is left to kill, you might be asking yourself. Well you would be right besides a bunch of made up underlings that Blizzard could keep coming up with their is nothing important left to kill.

Though fear not, Blizzard could come out with a Sin War game. This would be a angles vs demons game, the advantage would be it could be set up in factions so it would have the PVP elements that is quite popular. Plus it might be interesting to see some bad ass old testament angles. Ones with six sets of wings and swords of fire. This would be my hope, but in all honesty I don't know how well it would go over.