Bungie revealed that Season of the Arrivals will indeed have a live event to see it away but it won't be something major and hinted at when it might happen.
Destiny 2 will transition from Season of the Arrivals to Season of the Hunt, the inaugural one of Beyond Light, on November 10, 2020. Before that happens, we will see 14-hour downtime on November 9 which will be important for the topic of this article - the event that will see the current season out.
According to Luke Smith, there will indeed be a small event to close out Arrivals but it will not be something grandiose as watching Rasputin shoot out Red Legion's flagship out of the sky. This small event was supposed to be a surprise but an email let slip that we are going to witness something.
Smith didn't elaborate on what it would be but a safe bet says we will see Darkness encroaching on our home turf and the Tower will probably be a bit more sombre.
The head honcho confirmed as much - this location will be where the event will play out. He also dropped a hint on when the event would happen by saying "before the Lights go out". Now, he could be referring to the Darkness overcoming Traveler's light but he could also literally mean "when the lights go out" and refer to the aforementioned server shutdown.
That would put the time of the event just before the servers shut down on November 9, 2020, at 4:00 PM PST for Americas or November 10, at 00:00 UTC for Europe. Considering something will play out during the event, it is safe to assume it will start at least half an hour earlier, if not even more. then again, Bungie will most likely notify Guardians via their Twitter on how to witness the lights going out.