This is about as clear-cut as anticipation gets. Even the reader is looking forward to the Rebellion.
Literally, the animals proceed to have dreams. These dreams don’t sound terribly different than old Major’s dreams, either. And with all these dreams flying around, we’re thinking it’s the "dream stage."
We’re all extremely frustrated right now. What’s interesting is that, the animals aren’t quite smart enough to follow this tragedy trajectory themselves. So who does? The reader. That’s right. We go through the frustration stage (and the stages to follow), feeling for the animals what they aren’t quite capable of feeling themselves. So we’re using our own emotional reaction to gauge the plot’s movement. Which is so self-involved, we know.
Things have gone from bad to way, way worse in a way that resembles a boogie-man type nightmare. We identify as the nightmare stage the culmination of all things bad in Animal Farm.
What’s destroyed? Dreams. Visions. Any semblance of justice or equality. Why are all these things getting destroyed? Because, my friend, you are now in…the destruction stage. Such a fitting note on which to end a tragedy, isn’t it?