Foreshadowing is, at the end of the day, just a form of pattern recognition. Speculation is trying to guess at what patterns will be relevant in the future. One Piece has established that it is very methodical in it's storytelling, placing many pieces and characters way before they're highest point of interest comes.
Wonder at what will be significant is an important and healthy part of any serialized work. You never really want to leave an audience truly full. You want them to still think of your work once you've put down reading it, and it creates a desire to see certain narratives fulfilled. If people are speculating on what pieces of your story mean, it means they have personal investment. Not because they necessarily want to see their particular version of the story fulfilled, but because they are exploring. Searching for treasure.
It's a very good thing to have. And if someone becomes a little overzealous and puts out something highly improbable, that's just the nature of things. People will always go to extremes. I don't think it's particularly important, and the good theories tend to gain more fame as they go along, making them easier to find.