Based on a number of reports and a leaked installer, we can be fairly certain that Microsoft has a new version of Windows 10 in the pipeline. Windows Cloud is claimed to be another attempt to take on Google's Chromebook, however the information we have so far gives the lie to that suggestion.
Microsoft's partner Acer has already produced a line of Windows-powered Cloudbooks, which pack entry-level pricing and specs to match. These machines already compete on price with Google's offerings, so why a new Windows to do the same thing?
No, Windows Cloud seems like an updated take on Windows RT. The intention being to tie more users to the Microsoft Store and give developers an incentive to publish their apps there.
Ultimately I imagine Microsoft would like to remove support for stand alone installers across the whole of Windows 10. In doing so it gains technical and financial control over what gets deployed onto user's machines and can begin pushing a more iOS-like user experience for all Windows machines.
Cloud seems to be a terribly misleading name for this version, unless it will ship with limited storage and much better ties into OneDrive.
In retrospect Windows RT seems less like a flop and more like an idea ahead of its time. Microsoft seems to be pretty good at those.