The project is started in a separate magento-engcom/magento2 GitHub repository because Magento company wants it be implemented by third-party developers for free, and then the result will be merged back to the primary repository.
Kanban board for the probject: github.com/magento-engcom/magento2/projects/1
Documentation: github.com/magento-engcom/magento2/wiki/Technical-Vision.-Catalog-Inventory.