WARNING: The following contains spoilers for Episode 52 of Digimon Adventure 2020, "Dance of the Heavens, Hououmon," now streaming on Crunchyroll.
In the original Digimon Adventure anime, Agumon and Gabumon were the only two of the main cast's Digimon to reach Mega evolution. Though the rest of the main Digimon eventually reached Mega level in various movies and games, many fans have long felt disappointed that they never achieved these forms in the main story. But in the reboot series, Digimon Adventure 2020 that's about to change.
In Episode 50, HolyAngemon and Angewomon evolved into their extremely powerful Mega forms, Goddramon and Holydramon. Even in the original series, the angel Digimon were secondary only to Agumon and Gabumon in importance, but they were still unable to achieve Mega Evolution during their original adventure. Now, in Episode 52 of the reboot, Piyomon/Biyomon has become the next member of the cast to unlock their most powerful form, evolving into Hououmon in order to stop an exploding volcano. In the episode, the Crest of Love activates, allowing Garudamon to evolve when she and Sora, who had had a fight earlier in the episode, come back together and reaffirm their bond with each other.
With this development, it's almost certain that Tentomon, Gomamon and Palmon will reach their Mega evolutions in the episodes to come. Most likely, Tentomon will become HerculesKabuterimon, Palmon will become Rosemon, and Gomamon could become either Vikemon or Plesiomon -- Vikemon was used as Gomamon's official Mega Evolution in Digimon Adventure tri., but Plesiomon was used in multiple spinoff games, and the reboot hasn't been afraid to play around with the main cast's established official evolutions so far. In fact, tri. previously used Seraphimon and Ophanimon as Patamon and Tailmon's Mega forms, and the reboot's version of Agumon has Mega evolved into both WarGreymon and BlitzGreymon, so while it's likely that Tentomon, Gomamon and Palmon will have the same Mega forms that they did in tri., nothing is certain.
For longtime Digimon fans, seeing these forms in the anime will be a big deal. The original Adventure prioritized Agumon and Gabumon when it came to powerups, and while that's still true to an extent in the reboot, giving the other Digimon their own Mega forms puts them on more equal footing as members of the main cast. Plus, as Pegasmon, Ponchomon and BlitzGreymon have demonstrated, there's potential for any Digimon to have multiple options for evolution, so their fans can continue looking forward to seeing what they might become next.
