Zelnick said: "Both Grand Theft Auto Online and Red Dead Online will receive major updates later this fiscal year, featuring an extension to existing Frontier Pursuits for Red Dead Online, as well as Grand Theft Auto Online's biggest update ever, featuring a new take on Heists in a new location". There is a map of an island shown in the "HUD" of the video, though; perhaps this is where Doe has gone after feeling from Los Santos International? On December 15, 2020, we keep our eyes trained on the resort angle but ignore the Ocean's 11 stuff.
After the trailer dropped, Rockstar made a new blog post in which they laid out some new information about the event. Players will have to plan and execute a breach of Cayo Perico, one of the most secure private islands out there, evading or neutralising the guards and attempting to extract valuable evidence. Choose your crew - or even go it entirely alone.
The description implies that we'll most likely get to the new island via a submarine.
Additionally, the update on December 15 will bring new vehicles and tactical weapons, additional social spaces to hand out and party at, and a selection of new radio stations and DJs with over 100 additional songs. At the very least, the underwater vessel will come into play in some manner during the heist.