Godzilla defeats Ghidorah, Rodan is quick to accept him as the new alpha of the Titans.
As one of Godzilla's new minions, Rodan could be back for the sequel. If he were to appear, he'd be one of a growing number of Titans battling it out in Godzilla vs. Kong. Aside from the two titular monsters, Monarch will already have their hands full with Mechagodzilla and an Monarch begins its exploration into Hollow Earth.
Will Rodan be among them? It's possible that he'll be busy with other things when his new leader faces off with the King of Skull Island. One of the newspaper articles in the credits of Godzilla: King of the Monsters reveals that Rodan has flown to an island somewhere north of Fiji and has taken roost in a volcano. Prior to being woken up in Godzilla: King of the Monsters, Rodan was hibernating in the Isla de Mara volcano in Mexico. Now that Rodan has found a new home, it could be that he plans to resume his slumber.
If this is the case, Rodan may not appear in any capacity in Godzilla vs. Kong, even though, of the three Toho kaiju who made their MonsterVerse debuts in King of the Monsters, Rodan would be the easiest to bring back. Of course, pathways exist for both King Ghidorah and Mothra to be resurrected in the MonsterVerse, but Rodan returning makes the most sense, considering that he's now an ally to Godzilla. Nevertheless, that doesn't mean it will happen.
Rodan sitting out Godzilla vs. Kong would be disappointing for sure because it would deprive audiences of seeing the MonsterVerse recreate Toho's most iconic monster team-up. Godzilla and Rodan were an unstoppable duo in two classic Godzilla movies from the 1960s. King of the Monsters didn't have a chance to adapt this relationship since Rodan was on Ghidorah's side. The MonsterVerse has a chance to rectify this with Godzilla vs. Kong, but whether or not it will act on this opportunity remains to be seen.
There's a reason why the plan may be for Godzilla - despite his new title - to go into the sequel without any allies or minions. Sending him to Skull Island without backup isolates him from Titans who would stop Godzilla's fight with Kong from being an epic, one-on-one showdown. Also, when enemies like Nozuki and Mechagodzilla the fray, Godzilla may be forced to rely only on Kong for help, rather than one of his allies, and that could be the sort of finale the MonsterVerse is aiming for with Godzilla vs. Kong.
