It is likely that his presence will be detected through these intermediaries D2R Items, unless circumstances force his hand. Tyrael is still feeling the repercussions of the destruction of his Worldstone at the end of Diablo 2. This mystical object protected Sanctuary from Heaven and Hell, and he now stands as protector over the land on its behalf. Tyrael seems unlikely to lead any further charges into Hell or travel any further beyond what is known as the Pandemonium Fortress, where he may offer advice like Deckard Cain for those who choose to listen.
Five different Diablo classes that can be played were announced to date and they all offer takes on options from earlier games. In the sense that each installment has brought something new to the table The possibility is that Tyrael may become an element of the battle in the battle, helping to balance the sides by offering players the ability to gain angelic or demon-like powers in exchange for duties to Sanctuary. This kind of strategy could very easily build on the multi-tree expansion that was previously revealed for the series.
It seems unlikely that Blizzard plans to make Angels as well as Demons into classes as the franchise centers those stuck between them. But as the mortal truly stuck between Heaven and Hell Tyrael is in an unimaginable position in the entire Diablo history. He's more likely to play acting as a balancer in the story, or even an impartial voice, instead of embracing the side previously. Even when he is forced to buy D2R Ladder Items take the side of his opponent, Tyrael has come to understand what is important to mortals, which is the reason he'll be involved in the events of Diablo 4.