It appears in order to play Diablo 4 on your PlayStation console, you will need be online and potentialy to pay for the PlayStation Plus subscription, thus no offline mode.

This brought a lot of dissapointment to Diablo fans, as it was always fun to just farm legendaries even if your PS Plus subscription expired. There is still a chance that Diablo IV will just require the internet connection and not the PS Plus subscription, as Destiny 2 for example, where you still can play even with expired subscription.

Let's just hope that Blizzard's servers can handle the initial flow of users trying to start their game, as it will certainly contribute to overall impressions of the game.