Though Depp doesn't yet know if we'll get to see Dumbledore and Grindewald lock lips, he does know he needs to go right to the source: J.K. Rowling.
“My first port of call I hope is to meet J.K. Rowling and to talk exactly about that and who he is and who she wants him to be and learn a little bit more about her vision of this great man as a young man,” he told BBC London.
It's a good thing. Rowling has made a habit, in the post-Potter world, of manipulating her characters ex-post-facto. Dumbledore's gay! Hagrid's a half-dragon! Whatever! Though her books were pretty cut and dried, she's now inserted a bunch of things that frankly weren't there the first time around. Yes, Dumbledore's romance with Grindewald was hinted at, but only just. So it's possible that Rowling is literally the only person in the world that knows the "real" story about her characters at a given moment. Canny move by Law.