I think it's kinda funny that so many people seem convinced that Sakurai has intentionally been saying nothing about Ridley to keep fans salivating and is, like, hiding something regarding Ridley.
I think the unfortunate (for Ridley fans) reality is that Sakurai already gave Ridley all the pre-release attention he's going to and doesn't think he's anywhere near as important as fans think he is, or doesn't even think there's any actual mystery surrounding him. From Sakurai's perspective, he teased Ridley as the obvious stage boss for Pyrosphere and that's the extent of it; Ridley fans created whatever additional narrative has arisen from that ("Other M Ridley is the stage hazard, Super Metroid Ridley is playable!", "Sakurai is trolling us because he only showed Ridley's shadow!", etc.).
I'd be happy to be proven wrong, though. Ether way, it won't be long now!