Microsoft has confirmed that upgrade licenses to Windows 10 Pro that businesses obtain from the free preview of Microsoft 365 Business (M365) will remain in place. That's true even if the customer doesn't transition to a paid plan.
Also, companies that do subscribe to new Windows/Office suite combo when it's available, then later cancel the subscription or otherwise exit the plan, will be allowed to retain the Windows 10 licenses.
"Customers will be able to keep their upgraded license to Windows 10," a company spokeswoman said in an email reply to questions about M365 Business, including the preview set to begin on Aug. 2.
The confirmation that customers will preserve their upgraded licenses means that Microsoft sees M365 Business as yet another way to get Windows 10 onto more PCs. More specifically, Microsoft probably views the plan as a foot in the door, a precursor to the customer subscribing to the more expensive and inclusive Microsoft 365 Enterprise.