Existe, mas não é tão simples quanto inserir uma chave de produto atualizada, você também precisa da mídia.
When you buy/license Visual Studio 2015 Professional or higher, you'll have access to the install media, usually an ISO file or vs_setup.exe web-downloader. Mount the ISO image and run Setup and you'll be prompted to upgrade (if I remember correctly). You cannot (to my knowledge) have a side-by-side install of Community and Professional Edition (unlike you can with the Express editions).
Personally I would just do a full uninstall of Community first, then a clean install of Professional - when I worked on the setup experience of VS2015 I logged a whole bunch of bugs that were experienced during in-version SKU upgrades (e.g. upgrading Community to Enterprise, then downgrading to Professional), such as project template item templates disappearing, etc. It wouldn't surprise me if these still caused issues - I don't think it's worth the risk.