It isn't spoilers, it's just some fan prediction that was made before Fisherman Island, considering:
- All Birkan races have wings (or modified wings, in the case of Enel). So far, none of the D's have wings.
- We know what Poseidon is, and it isn't a cannon.
- No mention of Uranus
- No visual clue of these "20 soldiers that went to the moon" when the cover arc about Enel and the Spaceys occurred.
- It seems like a bad plan to entrust the poneglyph reading to the D's when only one of them knows how and others (the Ohara scientists) know how.
I do believe the D's and poneglyphs are related to One Piece, but this just sounds outright silly.