FYI, we just published the JupyterLab 1.0 release candidate to pypi (1.0.0rc0). Please test this, and if you have an extension, we encourage you to try updating your extension to work with it.
You can install it with:
pip install --pre jupyterlab. You can check the JupyterLab version from the Help > About menu item.
The current plan is to publish JupyterLab 1.0 in about a week. We will be updating documentation and the changelog and fixing a few small UX issues in the meantime.
You can see the list of issues and PRs closed in the 1.0 milestone at https://github.com/jupyterlab/jupyterlab/milestone/2?closed=1