in Splatoon 4 I definitely want to see

• more customization options for our playable characters
• continued focus on world building (more stuff like the Alterna Logs and chat logs with unlockable cutscenes)
• maps having different layouts in turf and not just ranked (maybe two versions but it also heavily depends on what kind of specials are brought back or introduced)
• experimenting with weather effects on maps. even something like the return of the sunrise skybox we finally got at grandfest being seen in the other hubs would be awesome!

I think we’re gonna get Splatsville and Inkopolis access in base Splatoon 4 with additional locations added so no need to worry about that. Apartments that give us a single studio room to decorate still feels like it’s attainable but could also be a DLC. they gave us WAY too many locker items and no save state for them if you want to revert to a previous design anyway! it could still be added since we have returning content updates until Summer Nights (potentially) so i guess we’ll see.

and as far as spin-offs go i would love to see something like Project Diva for Splatoon. building off what Squid Beatz has in terms of gameplay and giving us dance videos for the idols (like the Grand Festival screens at the clam stage) that are a little flashier. we get to unlock new locations and outfits which makes for a ton of replay-ability! and it could have a story mode too like Persona 4 Dancing All Night.

a single player only title focused on earth exploration feels like a pipe dream so I can see them going the music route since it’s such a core part of the game!