Summary:What happens to the history of workflows when a farm migrates content to 0365 platform. All the Workflow History list data will migrate, this data sits inside SharePoint but the Nintex History view of a workflow will be lost.
Product:Workflow for SharePoint 2010;Workflow for SharePoint 2013
There is no way to migrate Nintex Content DB data to the cloud (02/2016). The only way to capture this data is to create a SharePoint List/s that captures this information (A Nintex workflow could be provisioned to do this).
Having the data in an archiving list will insure it is still accessible in 0365 when the content gets migrated. This will also make the Archive data safe from maintenance tasks such as Clean up jobs and Purging.