Even if it's just a guess, it's incredibly difficult to be accurate, so what's the point?
I don't think anyone wants to reveal their Bitcoin holdings, and even if they did, would you trust them?

I don't think there's any point in sharing your Bitcoin holdings on forums, even with close friends or relatives. I think it's best to keep it private. There are still risks involved, and for security and convenience, it's important to keep it private.