Previously, repositories named would become GitHub Pages.However, the new format for User and Organization Page repository names is

While both formats are supported, we highly recommend new repositories use the format. If both a and a repository exist, the version is used.

You do not need to rename old repositories from the .com name to the .io name, as GitHub Pages will continue to route the old repositories. However, keep in mind that a .com name will send you to a website.