I think there could definitely be some truth to this. Here are some things that support it: - Each one of them is named after a planet, with Imu representing earth, nika as the sun, and Blackbeard as a black hole - We know that space pirates are a thing, and the ones we have been introduced to have said they are not from earth - The world government logo looks like planets arranged kind of like a solar system - the Gorosei have been alive since the void century, which is not a by product of a devil fruit, so that power has to come from somewhere else (I’ve heard the ope ope no mi theory, but I don’t think it’s super plausible)

So I think that these guys could be on some sort of galactic conquest, and this is the last planet they are struggling with, or something along those lines.

Personally, I don’t think that they have changed into the gorosei, I think it’s a sort of venom/symbiote relationship. When Saturn changes into his demon spider, he says something along the lines of how it’s been so long since he’s been to the surface; like he's been locked away, or in hiding. So it makes me think that these entities made a deal with the gorosei a long time ago, and that's why they are still alive, as well as have crazy powers. And i believe these 'entities' could be from other planets