The singularity seems to me reasonably inevitable.
Everything you have described suggests that we’re pretty far down the road of developing self-programming entities that behave, and evolve, like biological ones in certain limited respects. This is interesting, but not the same as ‘the Singularity’ which, in so far as it has been defined, is some nebulous concept about machines surpassing us in their ability to do whatever it is that the author describing it values about human consciousness, and therefore, for reasons that again are rather vaguely adumbrated, becoming our new robot overlords. None of which is even slightly inevitable.
As for nanotechnology, you may have noted it has already been designed by nature. There, it's called 'bacteria.' We have a model for nanoscale machinery right there. What, did you really think we'd make nanomachines out of METAL?!?
Of course not. But there is very little evidence that we will be able to make nanomachines out of anything at all. We’re still at the stage, as far as I understand it, of just about being able to poke atoms about and get them to sit in the right place for short amounts of time. Are you seriously suggesting that we’re anywhere near building anything that looks like a bacterium from scratch?
Retroviruses operate by changing the genome.
Well…they change whatever segments of it they happen to randomly recombine with when they insert themselves into the host genome, but you’re talking about them going for a particular, defined set of genes (a very, very large set, as I’ll discuss below) that are presumably being expressed only in certain organs
We now have a computer that ties into the impulses sent to your speech centers that can replicate speech. From speech centers, how long until other muscle centers? Obviously the voice box is a great deal simpler than the arm - but do you really think having done one, the other isn't simply a matter of refinement? From there, do you really think its so hard for us to make a machine that functions similarly to an arm?
What you’re presenting here, as far as I can see, is an uphill version of the slippery slope fallacy. The answer to your apparently rhetorical question is yes, yes I do think that such advances are more than a ‘matter of refinement’. Or, at the very least, I have no reason to think otherwise, and neither do you, because I’m guessing that neither of us are experts in the field of neuromuscular junctions or the even tricker world of proprioception.
Similarly with genetic engineering. We've done it on pigs, we've played around with plants for decades, the human animal isn't much different. We've mapped the genome. It's a matter of deciding where to poke. Obviously it'll take a lot of experimentation, but there's no reason to think it can't be done. We have all the technology. The 'millions of steps' are merely deciding how to apply it.
OK, I don’t know how much molecular genetics and biochemistry you know, but this sentence seems to suggest it’s not very much. We can, at the moment, by dint of great effort, get plants and animals to express a single foreign gene product under the control of a simple regulatory operon, or knock-out a gene or gene complex that the organism is already producing and view the effects
Having ‘mapped the genome’ means very little in terms of genetic engineering, particularly in terms of ‘where to poke’ (what does that even mean?). To illustrate the truly staggering gap between ‘mapping the genome’ and the sort of things you’re talking about, let’s take another of your early examples, the re-engineering of the human knee.
You want to reverse it? Fine, for starters you’ll have to get the developing embryo to grow its joint ‘backwards’ – that’s not a matter of turning the gene around, you’ll need to know how the carefully timed interactions of various concentration gradients at different stages of development affect joint symmetry. You’ll have to make sure that whatever you do to those apply only to the leg (is that even possible? Will the same mechanism that makes backwards knees force the poor tyke to develop backwards elbows? Maybe. I don’t know. Neither do you).
Half of what you’re trying to do might not even have anything to do with the sequence or map of the genome at all. It might not be a matter of taking out or putting in genes (which, let me re-iterate, is all we can do at the moment), but up- and down-regulating existing genes, using transcriptional and translational control factors such as sequence acetylation and micro-RNAs that we’re only just beginning to understand.
Say you’ve done that. OK, time to investigate the neurology. You can’t just ‘give me’ a backwards knee, any more than you can make me capable of flight by gluing wings on to my back. I’ll need to be wired up so that I instinctively understand how to maintain my balance, how to run and leap without breaking my ankles etc. etc. Which is a whole other problem.
This is not an extension of existing technology. This is not ten years of hard work. This is orders of magnitude out of our grasp. As far as I can see, there is no logical reason why we, as a civilisation, would direct our resources towards solving this issue (which is one very, very minor aspect of your transhumanist revolution), nor any reason why we would be successful in doing so.