At the time of writing this response the features timeline reflects yaml releases are coming 2018 Q3.
https://docs.microsoft.com/en-us/azure/devops/release-notes/
Update: This has been bumped a few times. Checking the comments below is recommended as folks have been providing updates as they find them.
Update
As per comments, this is now possible:
https://devblogs.microsoft.com/devops/whats-new-with-azure-pipelines/. The following is copied and pasted from the article and demonstrates using various stages:
stages:
- stage: Build
jobs:
- job: Build
pool:
vmImage: 'Ubuntu-16.04'
continueOnError: true
steps:
- script: echo my first build job
- stage: Deploy
jobs:
# track deployments on the environment
- deployment: DeployWeb
pool:
vmImage: 'Ubuntu-16.04'
# creates an environment if it doesn’t exist
environment: 'smarthotel-dev'
strategy:
# default deployment strategy
runOnce:
deploy:
steps:
- script: echo my first deployment