Several key contributors to the Migrate Initiative will be at the sprint at DrupalCamp Montreal on Sunday (and to some degree on earlier days as well). Join contributors Adam G-H (phenaproxima), Maxime Turcotte (maxocub) and Dave Vasilevsky (vasi) in person. Initiative coordinator Mike Ryan (mikeryan) is also planning to join remotely on Sunday.
Among the most important Migrate critical issues on the table that are planned to be worked on is auditing for potential ID conflicts before upgrading from older versions. This is the most thorny outstanding issue for the initiative. Use cases and feedback in general is welcome. Further migrate issues are categorized and tracked in the Migrate triage spreadsheet (update regularly). These include handling import of private files, adding back support for incremental migrations, redirecting for obsolete content translations when they are merged in the migration, etc. All of those need helping hands and this is a great time to get experienced with help from the most well versed people in the field.
If you cannot join the sprint this time, your involvement is more than welcome anytime. The migrate team has weekly meetings on every Thursday at alternating meeting times. See https://www.drupal.org/node/2735059#meet for the upcoming meetings.