The latest Diablo 4 cinematic trailer from Diablo 4 Gold Blizzard features Inarius looking down Lilith and armies on both their backs. While the scene does not mention Tyrael's direct involvementin the story, his creation of the Horadrim as well as his influence on the various Paladins of Sanctuary indicates that he's at work. Dark and light battle across the field, but now-mortal Tyrael is somewhere in between.
It is likely his presence will be felt through these intermediaries unless circumstances make him a victim. Tyrael is still feeling the effects of the destruction of his Worldstone at the end in Diablo 2.
The mystical artifact shielded Sanctuary from Heaven and Hell, and he now acts as a protector for the land in its stead. Tyrael is unlikely to lead any further expeditions into Hell or venture much further then The Pandemonium Fortress, where he may provide advice similar to Deckard Cain for those who choose to listen.
Five different Diablo classes that can be played have been released so far and all of them represent alternatives to the earlier games. Each installment has been different Perhaps Tyrael will be an active participant in the fight, balancing the sides by giving players the option to acquire angelic or demonic powers in exchange for obligations to Sanctuary. This type of strategy could easily follow on the multi-tree expansion that was previously in the game.
It's doubtful that Blizzard plans to cheap Diablo IV Gold transform Angels and Demons into classes, given that the franchise focuses on people stuck between them. But as the one who is who is caught between Heaven and Hell Tyrael is in an unusual position in Diablo story.