If I had to guess…

* Hangman is connected somehow to Iceman (similar callsigns, attitude etc.)

* Iceman is the one in the casket

* “Someone’s not coming back from this” could be a self-fulfilling prophecy for Maverick himself

I’ve read repeatedly that Iceman was serving as Chief of Naval Operations in the movie, but the brief glimpse of his picture indicates that Admiral Kazansky is commander of the Pacific Fleet, which is a more appropriate fit for the story considering the CNO is stationed at The Pentagon in Washington, DC whereas the movie is set mostly on the west coast.

After multiple delays, TG:M is set for wide release eight weeks from today. It’s been a long time coming.