that's not really the actual timeline. here is the pull request for adding union types.
https://github.com/Microsoft/TypeScript/pull/824
I believe all 3 teams, TypeScript, Flow, and AtScript, are working together for few things as is.
I believe all 3 teams, TypeScript, Flow, and AtScript, are working together for few things as is.
If you look at that TypeScipr PR, you see it closes an issue and they reference (2 months ago) Flow there.