There could be an improvement of Slack, so when a user adds another Slack team to one computer, it is also added to other computers where that user has authenticated, such as if they used a different e-mail address. The computer would know because of the group authentication of each of the e-mails on the other computer, that they were linked in a group.
There could also be an improvement that allows scripting to create rooms and other elements of Slack channels, to integrate it with other coding projects, such as a SDK.
There could also be single-sign on for both Microsoft and Google, as well as other services.