IMO automation, genetic engineering, implants and replacement of natural body parts by artificial body parts will start social, economic and medical revolutions within the next decade.
One of the worst misbeliefs is that the end of poverty (at least world hunger) and the end of large-scale wars (e.g. Middle East) is just futurist idiocy while it is actually achievable within a year with existing technology. But political priorities prevent it.
Anyway, my point is that effort is required to advance science and technology. To call it a dream and to do nothing to realize it is the wrong way. It only wastes time because the efforts and investments must be made anyway (by future generations).
> There is no way at the moment that we can sustain our current lifestyles without fossil fuels.
True. But again: There was and is not enough effort to create the technological alternatives. Besides, a lot of energy (and burned forests) could be saved by simply not eating animal products any more.
> In addition, if we remain unsustainable then we'll just grow to fill the next level unsustainability if a new technology did come along.
Humanity is always at the frontier of sustainability or possibilities for one reason or another. Science and technology lead to creation of resources (e.g. use of steel, use of fossil fuel, use of Uranium, use of solar power) and more efficient use of resources like e.g. man power (e.g. by better program languages, better programs, better computers, better cars, better houses) and less religious societies and less wars and lower birth rates.