The following post contains minor SPOILERS for Avengers: Infinity War.
The Iron Man 3 Blu-ray includes a sneak peak at Thor: The Dark World; the Thor: The Dark World disc features a glimpse of Captain America: The Winter Soldier.
I get not wanting to reveal anything about Avengers 4 before Infinity War came out; supposedly the official title was an Infinity War spoiler.
The longer the Marvel Cinematic Universe has gone, the more it has codified a set of rules that each of its movies follows.