Thank you for your continued feedback. We are currently working on this, and recently announced this feature for developers in Beta. For more information, please visit https://developer.microsoft.com/microsoft-teams/blogs/importing-3rd-party-platform-messages-to-microsoft-teams-is-now-available-in-beta/.
An error occurred while saving the commentNeil K commented
The only thing holding me back from migrating 65 devs to Teams is the loss of history in Slack. This should be a *very* high priority feature on the Teams backlog.