The Migrate API was one of the last initiatives in Drupal 8 and is still stabilising as we approach Drupal 8.2.x.

We all know the Migrate API is important and it was raised in New Orleans by Dries on the need to improve Migrate via better documentation, stabilisation and making it easier for common use cases outside of the upgrade path.

As one of the core maintainers for Migrate, i’d like to discuss:

Which areas are currently problematic and still needing attention?
Documentation
Upgrade UI
Multilingual
Drupal 7 to Drupal 8
What features would we like to focus on next?
Improved developer tools and runners
Users interfaces for running and building migrations
Improved performance
Drupal 8 to Drupal 8?
API Improvements
Better base classes for migrating from non-Drupal sources, current contrib tools
Abstracting the core of the API out into a PHP Library
Drupal 9.x ideas and more...