No. Speculation would be, "I think they might have done a musical episode, but with puppets. Kinda like Buffy AND Angel."
When the writer/producer Tim Minnear says that he was recruited by Whedon with the pitch for that episode, and you see that the structure of the episodes was built to foreshadow that episode, it's not just speculation. If Buffy had been cancelled one episode before Angel was 'revealed' as a vampire (um... spoiler?) would that have been speculation? Or both the planned outcome of the choices they were making, and, you know, obvious?
Is it possible that they might have changed direction? Sure. But there has never been any indication that they were going to.
As for why it matters to the critique, or my critique- the relationship dynamic between Inara and Mal is the worst aspect of the show to begin with. The idea that the resolution of Mal's inability to resolve his Madonna/Whore complex is to have Inara gangraped makes it go from slightly uncomfortable to grotesque. Again, IMO, YMMV.
The reason I didn't want to go to deep into this in the OP is that Firefly is fine. It's a decent show. I didn't write the OP to pile on to the show. I truly love Buffy and Angel. I liked Firefly and Dollhouse. But the things that, for me, make Firefly a standout (specifically- an absolutely stellar cast) do not overcome the issues that I have with it that become more glaring over time and that I cannot overlook. I barely made it through re-watching the last time, and that was before the Whedon mess came out.
If you love the show like Homer Simpsons loves donuts- unreservedly and with pink frosting, then such is your considered choice and I have no wish to disturb it.
EDIT- I wanted to make a slight caveat. When I say that the Inara/Mal dynamic is the worst aspect, I mean the Mal aspect. And I also think that the borrowing of Lost Cause mythology is arguably worse, for me. It may not bother other people who don't notice it or don't care.