Will Teams Channel posts be migrated?

Yes! The last 50 conversations will be in the "Posts" tab. All other (older) conversations can be found in the "Message History" tab.

Remark:  All messages in the "Posts" tab are now from user "Admin_Spikes" which was utilized to do the migration to the SD Worx Tenant. On the "Message History" tab, you can see who did the original message post.