Well, not very much of an idea as it happens. The trailer in question is more exposition that in-game footage – you're after a “cursed” diamond with a rather storied history.
It looks like the heist will take place in some kind of luxury estate, but it's hard to tell much from the illustrations shown. Overkill is remaining determinedly vague, too.
"Time to Shine. December 16. New heist: The Diamond. New crew member: Clover," reads the trailer blurb. Not super informative, is it?
According to the game's, “Day 1” will go live this Sunday.