"a being that is exactly like you in every respect—identical behavior, identical speech, identical brain; every atom and quark in exactly the same position, moving according to the same causal laws of motion—except that your zombie is not conscious."
As someone with a medical background, I find it very hard to believe this is possible. Not unless Consciousness is reduced to something so abstract and disconnected from what we consider our "Selves" as to render it almost meaningless. After all, traumatic brain injury can alter every aspect of your personality, capacity to reason, and ability to perceive. And if "consciousness" isn't bound up in any of these things, if it exists as some sort of super disconnected "Thinking thing" like Descartes seemed to think, I really can't see the value of it. It's like the Greek interpretation of the afterlife where your soul exists as a senseless shadow, lacking any concept of self or any memory of your past life. What good is an existence that lacks all the things which make it unique?
Then again, as a somewhat brutal pragmatist, I cease to see the meaning in having an argument when it seems to devolve beyond any connection to observable reality.
I think you're incorrect about the wave model when you say it doesn't take technological progress into account. I think what it assumes is that technology will either not progress fast enough to halt the downfall, or that the downfall itself will halt or hinder technological progress. After all, tech progress requires an environment with not only the luxury of time but also an abundance of materials. The exhaustion of certain material resources, the loss of trade with producers of certain resources, loss of communication with others in the field slowing the exchange of information, all these things could strangle the meaningful advancement of technology in the crib.
And all this also assumes that we could come up with and implement meaningful solutions in the first place. There is no guarantee of that. If, for instance, the downfall is triggered by a pandemic as is listed as one of the threats, there is no guarantee that we'll be able to manufacture a cure in time. And the loss of a significant portion of humanity would cripple our various industries. And this would cripple research and development by limiting the resources available to them.
Many people seem to forget that the advancement of technology depends on a complex web of supporting industries. Even something like an iphone requires materials and production steps that take place across the entire world, let alone the high tech components for something like an AI running supercomputer. I think the wave model is less a prophecy of doom that fails to take advancement of tech into account and more a prediction of the results of a truly catastrophic event. The idea that, as we struggle towards the singularity, something kneecaps us and we fall. And that this either prevents us from ever reaching that singularity or at least it greatly sets us back in our attempt to reach it.
Of course thats just my interpretation.