In joining with one of the powerful descendant of Tyrael, Tyrael eliminates the primary evils and Diablo 4 Gold takes the control of the Black Soulstone. After the Archangel of Death, Maltheal, went after the stone and turned on all of his companions Tyrael was the one to took his friend to Pandemonium to destroy death itself.
Tyrael is able to keep his mortal form . He then reconnects with his angelic friends to become both an Aspect of Justice as well as of Wisdom. Diablo 3 ends with him looking to see if his new mortal companion, who could be corrupted, could someday become the next threat for Heaven, Hell, and Sanctuary and even the life itself. Aspect of Justice and Wisdom Aspect of Justice and Wisdom probably won't stand by while Inarius marches an army upon Hell in search of his former love, Lilith.
The most recent Diablo 4 cinematic trailer from Blizzard showcases Inarius confronting Lilith Armed forces at both of their backs. While this footage doesn't include Tyrael's direct involvementin the story, his involvement in the creation of Horadrim and the influence he has on the Paladins from Sanctuary ensures that he's involved. Light and dark battle upon the battlefield and the now-mortal Tyrael is somewhere in between.
It is likely his presence will be experienced through these intermediaries unless circumstances cause him to act. Tyrael has a hard time coping with the aftermath of the destruction of the Worldstone at the conclusion in Diablo 2. This mystical object protected Sanctuary from Heaven and Hell and Diablo IV Gold he protects the land as its successor. Tyrael is unlikely to lead any further expeditions into Hell or travel any further then his current position at the Pandemonium Fortress, where he might provide advice like Deckard Cain to those who are willing to listen.