now as many people speculate there is the matter of tyrael, is he corrupted, possibly, but it is a little overused concept in games, but somewhat logical, if one is exposed to a contaminated substance of often becomes infected, in the case of tyrael it would be exposed to the corrupted worldstone. as you recall of the prime evils and lesser evils, only lesser evils have eluded us thus far, Belial Lord of Lies, and Azmodan Lord of Sin, now it was these two who banished the prime evils to the mortal world, and with the prime evils in the void, these two are prime candidates for ruler of Hell. now baal's soulstone is the only stone not to have been shown being destroyed at the hellforge in act 4, but since both mephisto's and diablo's stones were destroyed, why not baal's as well.

the prime evils are trapped in the void, in the burning hells, but as we all know no one is ever trapped in a void for ever, there are many examples of this is computer/console games and there subsequent expansions/sequels

the worldstone is destroyed, this allows more demons and of course more powerfull demons and demon lords to pour through into the world of sanctuary. Well in the movies and final speaches by NPCs in harrogath, it says the destruction of the worldstone will allow demons to more readily enter the world of sanctuary, and this is a problem, well for the people of sanctuary, it is a good thing for us, coz it means more games, more games being Diablo 3, and its possible expansion, then based on how that game or games end will dictate as to the existance of Diablo 4 and whether or not it will be a sequel or a prequel to the entire series, but im slightly getting ahead of myself.

Diablo 2 + lod