To help overcome that hurdle, Microsoft has released a migration utility that streamlines the migration process, Visual Studio Online Product Manager Ed Blankenship writes that the utility, which is free, "handles the most common scenarios" for migration which includes version control repositories and source code files, test cases and test results, work items, and mapping between on premises AD user accounts and Microsoft Accounts used in Visual Studio Online. The tool works with versions of TFS back to 2010, and there's no need to upgrade to the latest TFS version first. It's a step-by-step process for mapping team projects in TFS on-premises to Visual Studio Online team projects. Read more here.
Microsoft TFS to Visual Studio online migration tool released, compatible with versions 2010 and newer.