Gitlab for JIRA DataCenter

Are there any plans to release the current ‘ for JIRA Cloud’ as an Add-on for JIRA Datacenter? We have a significant number of Mercurial users (>500) we are expecting to migrate to GitLab, but at the moment they are used to having a Development panel in all of their issues, and there is a reluctance to lose that functionality with the migration, despite the advantages of the move. For security reasons we have to host all of our systems on premise, so the cloud implementation is not an option.