I am watching rockstar games since a very long time and i can conclude that the marketing phase has been begin since the start of the october month.
We all have seen the new decorated miami city and a NBA match on the night of November 18, before the release of GTA VI, rockstar has to prepare a good plan to release next gameplay trailers in this month since November is the final month of release and in that month they will most likely market only about to pre-order the game or buy the game.
So we will definitely see the next gameplay trailer of the game maybe in middle of the october month and I'm pretty sure the release of the next trailer is around after this week.
I'm not confident but i think it could be executed in this order.