The Drupal 8.3.x branch is getting ready to introduce a new experimental media module. This will bring enhanced media handling in Drupal 8. The closest solution in Drupal 7 to handle media is the file entity module. Now is the time to discuss migrations from file entity in Drupal 7 to media entities in Drupal 8. For core, there is already an issue for this, but for contrib... there is no migration. So, I wrote one.