The long road to the release of Dragon Ball Super's first movie has been paved with fan theories and speculation - which is admittedly all we have to go on until that next trailer arrives. Well, one theory about Dragon Ball Super: Broly is catching on with fans, as it predicts a truly exciting turn in the film's finale: an appearance from Super Saiyan 4 Broly!
As you can see in the theory that's sprun up over on Reddit, this fan is tracking both what we know about Dragon Ball Super: Broly from trailers, and what was revealed back when the film was first announced. The long-short of the theory is that Dragon Ball Super: Broly is being set up as a major fan service project; this canonized version of Broly definitely has a tail; and the first teaser trailer and posters have all depicted Broly as having eyes that echo the style of SSJ4 or Oozaru Saiyan forms (i.e., golden pupils in the teaser, and white eyes in the posters). It's a compelling argument - even if it doesn't turn out to be the least bit true.
Dragon Ball Super: Broly has been labeled as a fan-service project, and as such, it seems that fans have begun leaning in heavily on what kind of service they expect to see. As of now, it's expected that Goku's dad Bardock will show up, while there's a major growing theory that Goku and Vegeta will have to fuse and power-up to become Super Saiyan Blue Gogeta, in order to take finally take Broly down for good.
That latter point is an especially important detail, which may in fact connect back to this theory of Broly going SSJ4. The extent of Broly's canonized power level has yet to be clearly defined, which has led to much fan speculation about what Goku and Vegeta would have to do in order to take him down. Well, Dragon Ball Super: Broly bringing SSJ4 Broly into the fight would definitely present a highly-compelling reason for Goku and Vegeta to unite into SSB Gogeta. It would also be a great thematic finale, which builds directly upon the narrative arc that's been hinted at in Dragon Ball Super: Broly's synopsis:
"This is the story of a new Saiyan. Earth is peaceful following the Tournament of Power. Realizing that the universes still hold many more strong people yet to see, Goku spends all his days training to reach even greater heights. Then one day, Goku and Vegeta are faced by a Saiyan called 'Broly' who they've never seen before. The Saiyans were supposed to have been almost completely wiped out in the destruction of Planet Vegeta, so what's this one doing on Earth? This encounter between the three Saiyans who have followed completely different destinies turns into a stupendous battle, with even Frieza (back from Hell) getting caught up in the mix."
The key point here is that the story will examine "three Saiyans who have followed completely different destinies," which basically hints that finale would require Goku, Vegeta, and Broly in a three-way battle to go all out with their powers. After the events of the Dragon Ball Super anime, it's hard to imagine fans being thrilled by anything less than SSJ4 Broly or SSB Gogeta in the final battle - so maybe this theory isn't so crazy after all?
Dragon Ball Super: Broly will hit Japanese theaters in December, and is expected to arrive in the U.S. around mid-January 2019. Dragon Ball Super is currently airing its English dub on Adult Swim during the Toonami programming block Saturday evenings at 9:30 p.m. ET. It is also available to stream on Funimation and Amazon Video. The Japanese language release of the series is complete and available to stream on Funimation, VRV and Crunchyroll.