The only scenario that I don't find plausible is #4. Repressive governments may be able to slow technological advances, but they can't stop it.
A Singularity event is still the most likely. I'd lean towards a negative scenario though. The hyper-capable leaving behind those too hide bound to advance. A conflict then ensuing. It hits all the classical societal stress points for just about every metric you care to imagine.
Extropians and transhumanists have been knocking around ideas for failsafe tech limits, strategies for paradigm shifts, dealing with religious zealotry and objectionism, ect...
Fascinating topic...