I just noticed another one of my activities got migrated over from MB today. I only have a few...but here's proof that the migration process is still actually happening.
Millions of activities have been migrated. We are not dealing with millions of rows, but 50 billion rows. It is not a direct db to db migration; the process involves exporting the data in xml format from MB and re-importing it to Connect performing extra calculations and conversions along the way.