Will Jacob's wand somehow save the day when it comes to Grindelwald? After all, Dumbledore has an uncanny ability to predict when things will help (like the Invisibility Cloak) without necessarily explaining it in advance. One Reddit theory says Dumbledore giving Jacob the wand reminds them "of Dumbledore gifting the trio the snitch, the book, and the put-outer after his death. He knew they'd be useful even when they didn't." This would also explain the storm it looks like Jacob is generating from the wand in the trailer. Hmm, it definitely makes you wonder!
Image Source: YouTube / Warner Bros. Pictures