Blizzard first announced Diablo IV’s existence in 2019. It revealed a number of features that players are looking forward to, such as the return of the Rogue class. Even still, no one has seen footage of gameplay for the upcoming title until now, as someone has posted videos of Diablo IV gameplay up on Reddit.
Diablo III was released in May

Source: Hot Hardware – Huge Diablo 4 Leak Reveals Nearly 45 Minutes Of Gameplay Including Combat