Unity is not irreplaceable, and the breach of trust was not insignificant. Even with a 100% ideal response, they've given people a reason to think long and hard about if they want to commit to Unity for future projects. It will be a much slower death, but the end result will pretty similar.The "it's all over no matter what they do" doom posting going on is pretty over the top.
I know most forum posters know Unity as the 2010s asset flip engine, but many developers and hobbyist really like this engine, and for a good reason. It is a damn good engine. There's nothing quite like it.
If Unity decides to come out with a (seemingly) sincere apology and a proper, fair business plan along with a reasonable EULA, I have no doubt developers will keep using the engine. At least until Godot reaches maturity similar to Blender.
Now I'm not expecting a modern capitalist company to do that of course, but to say that Unity has no options to save themselves from this situation is just as foolish as charging 20 cents per install.