Large evolutionary jumps in mankind's history have always been associated with use of more energy per capita. The stabilization of oil consumption, visible since 2000, means one of two things:
a) Humanity has plateaued in its energy usage; or
b) Some other energy source is increasing.
Any of these means oil has hit a peak (there'll be no cliff, though, as you explained). The alternatives are not acceptable (evolution stopped or, for the first time in five thousand years, stopped requiring more energy use).
Large evolutionary jumps in mankind's history have always been associated with use of more energy per capita.
This is typical of the hand-wavy peak oil arguments.
An increased richness of culture or an increased scientific knowledge clearly don't require ever-increasing energy consumption.
Oppositely, the reason previous evolutionary jumps involved more energy per capita has been that ... cheaper energy has always previously available (ie, this a correlation, not a causation).
Edit: A modern laptop uses less energy than a desktop machine of twenty years ago, yet the laptop's user certainly experiences a somewhat higher level of "civilization" or whatever one would call it. Just a simple counter-example to "evolution always requires more energy per capita" claim.
You are proposing one of the possibilities I deem unacceptable, albeit without explanation. Without going about a huge text, you are proposing that for the first time in 5000 years, this chart will go flat:
a) Humanity has plateaued in its energy usage; or
b) Some other energy source is increasing.
Any of these means oil has hit a peak (there'll be no cliff, though, as you explained). The alternatives are not acceptable (evolution stopped or, for the first time in five thousand years, stopped requiring more energy use).