GitHub Actions will become a major player in the CI SaaS market. It can easily replace most CI tools out there especially if you ship code as container images. With GitHub Actions, you can do more than CI/CD. Most tasks performed today with bots (code sign validations, issue management, notifications, etc) can be made into workflows and run solely by GitHub.
Why would you give up your current CI SaaS and self-hosted bots for GitHub Actions? For one, GitHub Actions simplifies automation tasks by offering a serverless platform that is capable of handling most development tasks. As a developer, you don’t want to jump from one SaaS to another in order to diagnose a build error. The fewer environments you have to use on a regular basis, the more productive you’ll be. Not to mention that as a developer you probably spend most of your time on GitHub anyway.