Microsoft Office team today announced their plans to scale up the limits for Public Folders in Office 365. They announced that the folder count limit has been increased to 100,000 folders, a 10x increase over the prior limit as defined in the Exchange service description limits. Microsoft believes that this increase in limit will enable migration of larger existing public folder hierarchies and increased use of the feature in Office 365. As this is a cloud based feature, customers can immediately take advantage of this new scale for public folders.
As you scale the number of public folders in the service you might need to keep track of the number of folders. Exchange Online remote PowerShell provides an easy way to see the current public folder count in Office 365. Using the Get-PublicFolder and Measure-Object cmdlets you can readily get a current count of your public folders created in Office 365.
Source: Office 365