I argue in The Fourth Economy that we're on the cusp of a new economy. I don't argue that this is inevitable nor immediate. I only argue that it is necessary.
One key to this new economy is the need to adopt systems thinking as our new operating system, our new way of making sense of the world. In order to create a sustainable economic system, we'll have to create and re-create the systems that define us - systems like our energy systems, transportation systems, and political systems.
The transition from our current system could be like the transition from Roman Empire to the Renaissance. This transition was, obviously, punctuated by centuries of what we now call the Dark Ages..
Or the transition could be like the one from the industrial economy (what I call the second economy) to the information, or third, economy. That is, it could be so seamless that most people at the time don't even know that it is happening.
Of course, if you think that there is nothing unsustainable about our current systems, than the question of how we'll transition seems moot.