Ouch! I appreciate there are lots of components that need consideration with Teams but for M&A this is a nightmare. We can't federate domains to the new tenant and to drive adoption into Teams with no migration path is challenging. We can manually do the file data but the chat history in a Team / Office Group (which really can't be that hard to engineer??) is critical.
I'm delighted to hear that it will be coming in CY2019.
My only question is pertaining to the following: We are migrating in Jan/Feb when our subscriptions are up for renewal - would we be able to start on the new @xyz.com accounts in that period, and keep the old @abc.com accounts (data, conversations, etc) in hibernation until the migration tool/functionality is available? Or will Microsoft delete our old tenants conversation and data as soon as that subscription ends?
This is an issue, as we can't be expected to maintain both subscriptions until the migration tool is available?