Dumbledore Breaks The Blood Pact With Dragon's Blood
Dumbledore has done plenty of amazing things in his career as a wizard, but only three major accomplishments are listed on his chocolate frog card: "His defeat of the Dark Wizard Grindelwald in 1945, for the discovery of the twelve uses of dragon’s blood, and his work on alchemy with his partner, Nicolas Flamel." Two of these three have already appeared in the Fantastic Beasts franchise (or will appear, in the case of the duel), so it's very possible that the third will also be a part of the series as Dumbledore discovers that one of the uses of Dragon's Blood is to break a Blood Pact.
Although his discovery of the Twelve Uses of Dragon Blood was major, and is also mentioned in his obituary and the book that Rita Skeeter wrote about him after his death, not many of the twelve uses have actually been confirmed. Rowling has previously mentioned that one of the uses is as oven cleaner, and another is spot remover; extremely prosaic uses, really. It's not likely that Dumbledore would have become famous for discovering the Twelve Uses of Dragon Blood if they're primarily used to help people clean, though, so we have to assume that some of the remaining ten uses are a whole lot more impressive.
We also don't know exactly when this discovery was made - it's never dated in the Harry Potter books, which gives Rowling quite a bit of leeway when crafting the rest of the Fantastic Beasts story. So there is no reason that Dumbledore couldn't start working with Dragon's Blood as a way to break the curse. This would also tie into the Fantastic Beasts element of the franchise, as Newt would (presumably) be the one recruited to get hold of Dragon's Blood for experimentation. Finally, it has a nice symmetry - blood to break blood.
What This Means For Fantastic Beasts 3 (& Nicolas Flamel)
Fantastic Beasts and Where to Find Them was all about setting up a new corner of the Wizarding World, creating the lore of magic in America, and introducing the new characters that fans would grow to love. Fantastic Beasts: The Crimes of Grindelwald is all about setting up Grindelwald's evil plans and a few big questions for the audience (and setting fans on the path to that legendary duel). Now Fantastic Beasts 3 is supposed to be giving fans some answers, presumably to the Credence/Dumbledore mystery, but also possibly for Dumbledore, Grindelwald, and the Blood Pact.
We are sure to find out a whole lot more of Dumbledore's history and his time with Grindelwald (and, hopefully, a little less pussyfooting around the romantic aspects of their relationship) - and more about the Blood Pact as well. While the core conflict of Fantastic Beasts 3 isn't yet known, it's not likely to be the duel itself, given that there are supposed to be five movies in the franchise, but we'll definitely keep building in some backstory and moving toward that final fight. Which means we'll be spending more time on the Blood Pact and Dumbledore's attempts to break it - and possibly, his discovery of a few more uses of Dragon's Blood along the way. We may well see Nicholas Flamel again, too, as Dumbledore continues to work with him on the Blood Pact and the way that Dragon's Blood could help to break it. There's another character that may pop up as well; Ivor Dillonsby, who told Rita Skeeter that he had already discovered eight uses for Dragon's Blood when Dumbledore borrowed his notes.
Of course, there may be other ways to get around this Blood Pact that haven't yet come to light, especially as we know so little about this kind of magic. Assuming that the pact was made before Ariana's death, it does seem as though there is at least one loophole - as Albus, Aberforth, and Grindelwald all fought each other on that fateful day. Perhaps Dumbledore can exploit this loophole again (is it breakable to save a family member's life? Could Credence be the family member that Dumbledore tries to save?). Perhaps something else will pop out of Newt Scamander's suitcase to help or that Dumbledore will be able to figure it out in some other way. Only time will tell, but this is sure to be a significant part of Fantastic Beasts 3 and onward.