I slowed the part where Ed goes into the gate down to see what the images he saw this time were.
I noticed that he sees
-Al's body being taken away
-Ed doing alchemy with a bunch of smoke behind him (future? looks familier though.)
-Al with the Philosiphers stone in him.
They also show Hiroshima but not the clip they show later. They show the a-bomb dome.
Then I remembered having slown down the episode where we learn why Ed can do a transmutation without a circle. I also remembered thinking "I don't recognize those clips". So, I slowed went back and slowed it down again. I saw two clips that I couldn't remember seeing in any episodes. I have a pretty photographic memory too. Here they are:
They COULD be hints but I'm not sure. If you recognize them from an episode let me know.