Unfortunately, Marvel Studios has protected Avengers 4's secrets as if the fate of the universe itself was at stake. Just over five months out from the release date, Marvel has yet to release a trailer, unveil any imagery, or officially confirm which characters will be participating in the film, not to mention what Avengers 4's title actually is. Naturally, this has started to frustrate fans who don't understand the fundamental process of movie marketing, especially for a movie on this scale. It's worth pointing out, though, that no "delays" have ever actually occurred, as no date for the trailer's arrival was ever announced. Eager fans seem to be arbitrarily picking dates, and expecting the trailer to appear. That said, it's known for sure that Avengers 4's trailer will arrive before the end of 2018, as Marvel Studios boss Kevin Feige confirmed that fact in October.
However, there may well be two (or more) MCU trailers that debut in December, as the stars appear to be aligned for fans to possibly get Spider-Man: Far From Home's first trailer as well. For starters, Sony Pictures is set to release Spider-Man into the Spider-Verse on December 14, and there's no more natural a choice to pair Far From Home's trailer with in theaters than another Spider-Man film. Outside of the obvious logic of Sony - who fronts the money (and handles the marketing) for MCU's Spider-Man solo movies - wanting to pair Far From Home's trailer with Into the Spider-Verse, doing so would also be following precedent when it comes to time of release, as the first trailer for Spider-Man: Homecoming debuted in December 2016 before its summer 2017 theatrical arrival. That would line up perfectly again for Far From Home.
Of course, there's a glaring issue involved with releasing any kind of footage for Far From Home, that being Spider-Man's being dead in the MCU. Fans last saw Peter Parker as a pile of dust, and it's still entirely unclear how he gets resurrected in Avengers 4. With Marvel's pattern of intense secrecy around everything Avengers 4, it's quite possible none of the currently dead heroes are seen in trailers or other pre-release promotional materials, in order to preserve the mysteriousness of the plot. That means that Far From Home's trailer will just have Peter alive again, and also won't be able to explain how he got that way. Sony's marketing department is, therefore, trapped within a web of convoluted MCU continuity.
Finally, in addition to the likely December release of trailers for both Avengers 4 and Spider-Man: Far From Home, there's a smaller - but still possible - chance that the full trailer for Captain Marvel shows up soon too. There's a much lower level of certainty around that one, though, as no December movies really stick out as a logical pairing with Carol Danvers' solo debut. However, it's possible Captain Marvel appears prominently in the Avengers 4 trailer, which would make Marvel want to promote her further via her own trailer not too long before or after the Avengers 4 trailer hits.
- The Avengers 4 / Avengers: Endgame (2019) release date: Apr 26, 2019
- Captain Marvel (2019) release date: Mar 08, 2019
- Spider-Man: Far From Home (2019) release date: Jul 02, 2019