Is intelligent, sentient life likely to evolve anywhere life develops and has 2 billion or more years to progress?

Do you think increasing intelligence and thus eventual emergence of sentience is a standard property of life where ever it evolves provided it has sufficient time, a favorable environment, and the necessary resources?

We are just beginning in earnest to search for Earth-like exoplanets. Already, we are finding that they appear to be much more numerous that we had previously thought. How likely is it that Earth-like exoplanets of sufficient age and environmental stability will harbor alien life? Do you think we will find intelligent aliens living out there? How different from us would you expect an intelligent alien life-form to be?

Understandably, this question calls for conjecture. So feel free to take a SWAG at it. But to the degree you can, please provide the underlying science you base any wild-ass guess on.