So as I originally stated I think the most PROBABLE scenario is that we continue to have exponential growth for near term. Any economic model should be based on the most probable scenario don't the collapse of civilization as we know it.
So my assumptions about your beliefs are wrong but the reality is even worse... you are only planning on the now and current and not something viable for hundreds of years and hopefully longer.... I don't let the short term now greed and impulse factor cloud my judgement that the world needs something better that will last well beyond my lifetime. Making a buck now is great but giving something that gives my great great grand children a better chance at a good economic future and freedom is far greater.
With all due respect, planning thirty years ahead is problematic to the point of intractability.
Planning for hundreds of years ahead borders on delusional - consider the world of 1911, and you will realize that our not so ancient past is more alien to us that most "alien civilizations" contrived by science-fiction authors (even good authors), and this process is accelerating.
It is not unlikely that our grandchildren will be almost incapable of relating to us and our concerns due to changes in lifestyle and psychology (the inverse will also be true)