It's not just about staying at a particular version. It is about being able to find the version that matches what you are using. I recently started an new project using bootstrap and had to downgrade to v3.0.3 due to some incompatibilities. I have no idea how I would go about finding the matching type definitions from definitely typed. Their version numbers don't match bootstrap's (http://www.nuget.org/packages/bootstrap.TypeScript.Definitel...).

Also, how will the Definitely Type project be able to handle a fix to the definitions of an old version that doesn't apply to the current version?

Like jstclair I appreciate their hard work, but I think they really need to change their approach soon to avoid a lot of pain down the road.