It's not clear of such a service is coming in the near-future, it could be that Microsoft is just playing defensive by claiming the trademark to make sure it is not taken by another company. Neowin for instance expects the chances of a Windows 365 are pretty slim given the strategy Microsoft is following with Windows 10:
But, seeing that Microsoft has announced that Windows 10 will be free, for anyone upgrading from Windows 7 or 8, 'Windows 365' did not materialize in the way that many had speculated.
Even though Microsoft has not fully detailed its Windows 10 pricing strategy, such as what does a license cost for someone building their own PC and after one-year, what is the upgrade charge for Windows 10, we do not believe that Microsoft is targeting an annual subscription charge for Windows, at this time.