The official website for FMA: Brotherhood move has recently updated itself with a 15 seconds teaser. The movie, titled as 「Fullmetal Alchemist: Milos no Seinaru Hoshi」 is slated to debut all throughout Japan next Summer. You can view the trailer from their official website too.
Judging from the teaser itself, the movie is unlikely to pick up from the series ending itself. However, 15 seconds is just way too short to do any sensible speculation of the movie’s plot, although the continuation of the series from the ending is definitely impossible as Edward is still able to use alchemy.
The movie’s description promises that it will “finally tell the story of forbidden bonds”. If you ask me, it sounds like something straight out of a BL description!