Metroid needs a BotW style rehaul. I'm sure Metroid fans just want a by the numbers Prime sequel, but I think the franchise has hit a ceiling that desperately needs to be smashed through.
I think BOTW style revamp with more verticallity and caves and stuff could work, but it would also feel rather empty.
The problem with metroid is, almost all places samus visits are dead.
You only find the aftermath of civilized life having lived there and died.
We didn't really have a big number of NPCs in the series.
I don't think they could really work past maybe with a sole surivivor like with the Luminoth in Prime 2.
The other Hunters in Prime 3 were awesome, but you can't really fill a big open world with them.
Metroid needs to be smaller I think.
At least in map size.