DoctorOfSpace, if neither humans and AI are discriminated against, an AI revolution is unlikely. If an AI revolution is inevitable, it will probably be delayed significantly by equality between humans and AI though. But AI is probably a bad idea if it can wipe us out.
Also,
From my own understanding of life and the universe my assumption is less than 1 per 500bil stars. I suspect larger galaxies may have more, but then again they are more active so perhaps civilizations get wiped out more often.I think rare Earth is the most logical view. Earth has far too many special variables so of course we find ourselves where it is possible for us to exist. While most of science is supported by mediocrity, Earth is most likely one of the few special things we have from all the countless unlikely events that allowed intelligent life to evolve and become technological.
My guess is that around 1 out of 1 billion planetary systems has sentient life, but this is just my guess, and i am probably very, very wrong.
The amount of planets with sentient life depends on the definition of the word "sentient". Human-level sentience is probably very rare, but if animals like a fish or so are defined as sentient, the number of star systems with sentient life could be as high as one out of 10.000 or higher
Space is too big to understand, so do not try to understand.