IMHO CI/CD will need a different approach in the serverless world. One that reuses know and tested concepts from current best practices and adds its own requirements
- Semver all the things, not only Functions, also, queues, buckets, etc.
- Immutable deployments
- Manage deployments as graphs, following the same blue/green deployment approach. In a serverless world we could have blue/green/gray/purple/<whatever> as a combination of services running the same stateless functions in different arrays of versions equivalent to a canary deploy (as long as the infrastructure can properly tag and route users)