Thank you for the compliments, and apologies for doing my usual "say what happens to pop into my head" thing regarding your presentation.
Regarding Humanity 3.0, note the question mark in that section's title, and the multiple conditionals and branches in that part of the scenario. If I had to bet on whether human-like intelligence and consciousness are possible on non-organic substrates, I would say yes, for lack of any convincing counterargument. But something may yet come out of left field.
Your suggestion of a mind which "shifts back and forth between biological and electronic" is curiously reminiscent of something an old friend suggested a few days ago, but I wouldn't know how to turn off the organic part and then back on (the main problem being the second step...). My own preferred scenario would be gradual substitution of organic circuits with artificial ones without ever interrupting or duplicating consciousness.
If Humans 3.0 are possible, they would still not be a final goal, at least not in the form described. But I wouldn't worry about them taking over our world, for the same reason that I rarely get into fights with birds over who gets to eat a particularly juicy worm.
Essentially, I don't expect Humans 1.0 to get much beyond Earth, or Humans 2.0 to get much beyond the solar system. Maybe the nearest stars, if they really push it. But a Human 3.0 could realistically aspire to go anywhere in the galaxy and beyond. Why bother with the very special niches required by organic life forms, if you can go to the galactic center and feast on energy densities which would kill them instantly? Let them eat their worms.
If I must worry about takeovers, I would worry about Humans 2.0. They will still need relatively scarce water and carbon compounds, just like us, and they will be nearby. The day could come when they raise the question why Earth's inhabitants insist on making such poor use of their most valuable natural resources. Some 98% of my body mass is pure animal. If we insist on staying like this, we may eventually have to produce credible deterrence against our neighbours in space.
As for market testing, I think we are seeing the results already, at least as far as FQXi is concerned: a nanny-state dystopia might be acceptable, but dropping the Cro-Magnon body is so completely out of the question that it doesn't even deserve to be rated. :D