The first point I'll agree with; Sakurai did heavily imply Ridley to be a boss in that section.there are some other things to consider however, such as in the smash bros direct where Sakurai said "and dr wily's stage won't be the only one with a boss" and then there was a screen showing the metroid stage with a ridley shadow—or the fact that the hole in the back of the stage was certainly caused by the Ridley that is currently flying around above the stage and that's not something playable characters do. As much as I want Ridley in this game, it's obvious that that won't happen
However, I am actually quite sure that the hole is not created by Ridley flying through it. If you recall, the game introduced what are referred to as "Final Destination" versions of stages. Simple, flat versions of the stage without any hazards present. If you take a look at the Final Destination form of the Pyrosphere, you'll notice that the hole you say Ridley certainly creates is still there. This leads me to the conclusion that the hole is never created; it's there on the stage from the beginning. Could Ridley still come flying out of it? Yes, but he's not breaking through the wall when he does.
It's also interesting to note that the lava pouring out of the wall in the background is removed in the Final Destination version of the Pyrosphere. This may indicate that lava is actually a hazard on the Pyrosphere. It may not mean much, but having a stage where both lava and a space dragon are trying to kill you could be a little too much.