With Charjabug, Vikavolt and Togerodentwhatever, may we see an Electric-type first gym? Tapu Toko (sp?) is the deity of the first island, and it's Electric-type as well. It would fit the islands culture. Aside from those four new Electric-types, we also know that Hau uses a Pichu against you and that Pikachu is available on the first route. This very much hints towards the first gym being Electric-typed, though obviously, there's no confirmation yet. Oh, and there isn't a Rotom in your pokédex for no reason. Melemele really is focused on their Electric-types.
Electric also has no weaknesses to Grass/Fire/Water, and would just be super-effective against Popplio. Which isn't a bad thing, as most first gyms have a type they're strong against (Rock x3 > Fire, Flying > Grass, Bug > Grass), it's time for Water to be considered as the hard-level for once.
That being said, Bug/Electric and Electric/Steel would make it very easy for Litten users, while Popplio users are toast and Rowlet users are walled completely.. Hmm...
Edit: Togehedghog might not be on the first island.. It's Electric/Steel-combination makes it seem as if it would be at a construction site or something.. like that rocky terrain in the south east of the icemountain island.