Microsoft is hiring for their Windows as a Service development, & as that comes to light there's more discussion on-line, meaning you're more likely to see WAAS mentioned. Briefly it's not necessarily cause for alarm -- you don't have to start looking to invest in Apple hardware or learn *nix, at least not yet.
Think 1st of accessing the same web sites on your cell &/or tablet that you visit with your laptop or PC. Think 2nd of remotely accessing your PC. Now put the 2 ideas together, remotely accessing your PC using any type of hardware -- PCs, Laptops, Cells, & tablets -- & then take it a step further, putting your PC in the cloud rather than in a box on your desk. This is taking the Google Docs & Chrome OS concepts & applying them to the desktop.
Taking a page from the fashion world, what's old is new again. Decades ago mainframe computers did all the work, while you accessed them from dumb terminals located in-house or spread out around the world. Independent PCs, often connected to central servers took their place, but the basic idea of cheap hardware accessing a central, tightly controlled computer or computers has been tried repeatedly ever since -- why have a full-fledged PC when you don't have to? It's never caught on, but now things have changed.
The 1st thing you need is some sort of OS to run the hardware you use, at the least something like Google's Chrome or Android, or as Microsoft would prefer, win8.1 RT or Phone. Or you could use a full Windows install -- the idea is to access all of your stuff anywhere, not necessarily neuter your hardware. Relying on servers to run your software will never work when you want & need a real PC, at least not yet -- the pipes connecting you to the servers are simply not fat enough. If it were possible then Microsoft & Sony wouldn't have released their new, high priced game consoles, which they don't make all that much money on [if any] BTW. Instead they'd have released something on the order of Amazon's Fire TV, with tons more customers paying for the same XBox One & PS4 games [where they do make money] on-line.
My favorite example of where this sort of thing would work well is at a medical center or hospital. Docs & nurses would have their own personalized desktops that they could load with the info & data & patient records & notes that they need for that day or week or whatever. Then throughout the day as they work from room to room they can call up that desktop on anything from a cell to an exam room's PC. Patient records would be arguably safer, mistakes might well be reduced, & the time you spend waiting in the exam room would hopefully go down -- no more waiting for the nurse to come back with the doc's orders or an Rx etc. Push any phone calls & messages to the doc's desktop, & patients might not have to wait hours or till the end of the day for a responce to their questions.
That all said, while this has little or nothing to do with a subscription pricing model like Adobe has moved to, Microsoft could well decide one day that instead of selling you a license for a copy of Windows, they'll only sell you a month's or year's worth at a time. Right now the part of a subscription model that's *maybe* most attractive to Microsoft is no more Windows XP [or win7] holding on forever. ;)