When is the 'account switcher' feature supposed to be available for Office 365 Outlook?

At the MS Ignite conference this past week, Microsoft announced that one of the features in Outlook Pro Plus for Office 365, would be an 'account switcher' tab down the left side of Outlook, to allow users to quickly switch between multiple accounts under a single Outlook profile.

I'm not seeing this feature yet available to me, although I do have the new cleaner ribbon UI, so I know I'm receiving current updates.

Is there an ETA on when the 'account switcher' feature is going to be available for Outlook Pro Plus (Windows) users?