Spoiler alert: this question arises from the movie Fantastic Beasts and Where to Find Them, so if you didn't watch it yet and don't want it spoiled, stop reading. I also apologize if the question was asked before, I wasn't able to find it.
Near the end of the movie we see Percival Graves (a.k.a. Gellert Grindelwald in disguise) battling multiple MACUSA officials in the underground and slowly gaining the upper hand (not surprisingly, since he is basically the second best wizard alive). He is, however, stopped by Newt Scamander with the aid of a flying beast (forgot its name at this point), disarmed, and sentenced to death.
Since the movie implies that Grindelwald was already on a rampage throughout Europe before coming to the USA and assuming Graves's identity (the year is 1926), it's very likely that he was already in possesion of the Elder Wand, i.e. he already stole it from Gregorovitch.
We also know that he and Dumbledore battled in 1945 (19 years later) and that Dumbledore won both the duel and the Elder Wand. From there on we know the rest of the Wand’s story.
My question is: how is Grindelwald in 1945 still in posession of the Elder Wand if he lost it in 1926, when he "lost" to Newt Scamander? We know that one need not win an actual duel to win over the Elder Wand, or that the wand itself doesn’t even need to be present (examples of this behavior include Grindelwald simply stealing the wand from Gregorovitch, or, even more to the point, Harry "defeating" Draco and winning the wand by simply outwrestling two wands from his hands in Malfoy Manor), which is important since Grindelwald used the real Graves's wand as a part of his disguise and the Elder Wand is hidden somewhere else.
Is it also possible that this is a subtle, but profound clue that Grindelwald and Scamander will duel again, and that this time Newt will lose? This seems to be supported by Grindelwald saying an ominous (foreshadowing?) sentence while being taken away: