Here’s a brief outline of the status of the various parts of the block directory project.
The design of the Block Inserter within Gutenberg has gone through detailed explorations and iterations. The installation flow has been handed off for implementation. There is still some ongoing discussion around how to handle missing blocks and other error states. Mel has also explored some ideas for managing blocks within wp-admin.
Implementing the Block Inserter is in progress in the form of a pull request. Some internal architectural changes are underway, but that’s testable now by anyone able to run a Gutenberg local environment.