I think there will be some working groups established which will deal with topics covered in some do-a-thons (e.g. Julia Energy Opt…, Common Energy Data Format…). So far it there is no intended template (sub mailing list, sub wiki, repository on gitlab…) for working groups, is there?
I would be happy if it is possible without doubling up infrastructure. But additionally to the forum and wiki, at least a file sharing with versioning and an issue management system is needed.