If you are an early customer of Office 365, you probably are using the public website.
As you are (or should be) aware, public website are no longer offered with Office 365 and existing public sites are going to be deleted.
That said you can postpone this deletion until March 31, 2018 – giving you one additional year to move from Office 365 public website to a different hosting service.
Microsoft should come later with some migration scenario/recommendations.
To postpone the public website deletion, go to your SharePoint Online administration portal and reach the Settings section and select I’d like to keep my public website until March 31, 2018