Diablo 3 gets deep into Tyrael's story, as he becomes"the Fallen Star by tearing off his wings, and then falling into Sanctuary with Diablo IV Gold the descendants Nephalem dwell. As he joins forces with a powerful descendant, Tyrael banishes the Primitive Evils and gains control over the Black Soulstone. The moment the Archangel of Death, Maltheal, went after the stone, and then became angry with all his followers, it was Tyrael who brought his partner to Pandemonium to destroy death itself.
Tyrael chooses to keep his mortal form but is reunited with his angelic brothers to transform into The Aspect Justice and of Wisdom. Diablo 3 ends with him looking to see if his new mortal counterpart, who could be corruptedin the future, could eventually become the new threat in Heaven, Hell, and Sanctuary or the very existence of life itself. It's clear that the Aspect of Justice and Wisdom likely won't sit idly by as Inarius marches an army upon Hell to find his former love, Lilith.
The most recent Diablo 4 cinematic trailer from Blizzard includes Inarius confronting Lilith as well as armies at both sides. Although this trailer does not show Tyrael's direct involvement, his invention of Horadrim and involvement with the Paladins of Sanctuary implies that he's definitely at work. Dark and light battles in the battle, and the sadly dead Tyrael sits somewhere in between.
It is likely his presence will be perceived through these intermediaries unless circumstances require his intervention. Tyrael still feels the repercussions of destroying the Worldstone at the end in Diablo 2. The mystical artifact safeguarded Sanctuary from Heaven and Hell and he stands as protector over the region in its place. Tyrael appears unlikely to lead any further journeys to Hell or travel any further in to the Pandemonium Fortress, where he might offer advice similar to Deckard Cain to those who choose to listen.
Five classes playable in Diablo 4 Gold have been released so far, and they all represent different versions of the previous games. In the sense that each installment has brought something new to the table Perhaps Tyrael will be a player in the battle to balance the two sides by giving players the chance to acquire angelic or demonic abilities in exchange for duty to Sanctuary. This sort of mechanism can easily be implemented on the multi-tree advancement already confirmed for the series.