If / When we make the move it will roll out in phases and not be a hard switch. Even then the Slack would probably remain for a few months while we phase out certain channels and eventually all of them but the #general which is locked to Strapi employees to give notice we have moved.
Another community from a tool we at Strapi use called Orbit did something similar that we will probably base the move on. You can see their blog post about it here: