Well, I'm guessing it's on Isla de Mona.
I like the idea of Rodan having a volcanic origin once again. Rodan is such a great, classic monster from the series, and the original 1956 Rodan still really holds up great over time. But it seems like Rodan really kind of got overlooked over the years as the series went along, certainly moreso when compared to some other big-name kaiju like King Ghidorah, Mothra, or Mechagodzilla. Rodan had an okay supporting role back in the 1993 Godzilla vs Mechagodzilla, which was quite a while ago now, but really all he did in that movie was get his ass kicked first by Godzilla, and then by Mechagodzilla. He had a couple nice moments in Godzilla Final Wars, but of course he was just a face in the crowd there. I do miss the old days of Ghidorah, the Three-Headed Monster and Monster Zero, and it would be great to see the return of a more "classic" Rodan, if that makes sense!
Also, I really do hope in this new movie that both Rodan and Mothra aren't just enemies of Godzilla as well. They can maybe butt heads at first, that's fine, but I really would like to see all three team up against King Ghidorah. Maybe that would be too "predictable" or seem like too much of a direct copy of Ghidorah, the Three-Headed Monster for some, but that's another thing that for me was fun in the classic Showa movies, was that Godzilla actually had some monster allies and friends, and wouldn't always just fight everyone. It seems like that got lost along the way in the Godzilla series, too. Outside of Godzilla receiving some brief assistance from Mothra in Godzilla Final Wars, I can't think of a single other instance during the entire Heisei or Millennium-era movies where Godzilla seemed to have any allies at all. Especially now in this MonsterVerse, this is actually the most heroic take on Godzilla we've seen in a very long time, so I think it would work really well to bring back the idea of Godzilla having some kaiju allies.