Thank you for your feature request. If you're referring to the self-hosted TFS, this is something we're planning but not in the near future.
If you're referring to Visual Studio Team Services (VSTS), this is something we already do. You can view the instructions for the VSTS integration with Raygun here: https://raygun.com/docs/plugins/visual-studio-online
With the VSTS integration, you can create new work items from a Raygun error group, or link with an existing VSTS work item. Bi-directional updates are not currently supported, but this is something we can look at.
Thanks for your suggestions and feedback!