Although most of the existential risks that get discussed involve human extinction, it may be possible for events or processes to prevent humanity from achieving most of its potential without being made extinct. For example, future technologies might allow an oppressive totalitarian regime to perpetuate itself indefinitely. Alternatively, if space colonization is necessary to realize most of the future value of humanity, a disaster that does not cause human extinction but prevents humanity from developing the technologies required to leave Earth would constitute an existential risk.
Bostrom, Nick. 2002. Existential Risks: Analyzing Human Extinction Scenarios and Related Hazards. Journal of Evolution and Technology, vol. 9, no. 1.
A paper surveying a wide range of non-extinction existential risks.
Tomasik, Brian. 2016. Risks of Astronomical Future Suffering. Foundational Research Institute.
An article exploring ways in which a future full of Earth-originating life might be bad.