I'm new here, but I probably won't stay long if this mindless arguing is common...
It's important to stay open minded about these clouds. If you believe the clouds are nothing, but act as if that is a fact, you are not gonna get very far. If you think the faces confirm characters such as Ridley, but act as if that is a fact, you are not gonna get very far either. Consider both sides, and shut up about grammar.
I think the problem with the "they're just clouds" argument is that they are not just clouds. The clouds are artistic creations made by the developers in the game. They aren't just random shapes you see when you look outside, the developers made them to look that way. It is possible that they created the clouds without knowing they made them look somewhat like potential characters in the game, but what are the chances of that? Also, dark, ominous clouds (sometimes with figures in them) are always a sign of disruption in classic literature, which is exactly what's going on in this "story." In my opinion, these clouds are far from just figments of our imaginations.
The only characters I see are Bowser and Ridley, and I'm not completely sure about Ridley. I think once we see this cutscene in motion we will be able to tell. Until then, nobody is right.
But if these clouds turn out to be real, Ridley will be in the game (mostly likely as a playable character). I do think Ridley will be a character, even without this cloud speculation. This is just my opinion though.