This is still disappointing, all these years later. Everything was set up so carefully, and then, Whoops! Look, a way out! Strikes me as very deus ex machina.

And anyhow, why didn't they forcibly sedate every human until after the change? Then if they decided it wasn't worthwhile they could choose to die then.

And anyway what person would choose pain, embarrassment, and romantic angst over untranslateable 2 anyhow?

Edit: that came out very negative sounding, sorry. Three Worlds Collide (with the normal ending) is my second-favorite story, second only to The Fable of the Dragon Tyrant. It teaches me so much.