How could that work though? A pick-and-choose system would create a software equivalent of the vast variety of PC hardware, which while advantageous in some ways has been a huge headache for MS and technical staff to support, and lead MS to try very hard to limit and control the PC hardware architecture. An explosion in the number of possible software component configurations in the base OS is a support, stability and security nightmare in the making.
Unfortunately Linux already has something like this already, in the form of the tens of thousands of packages available and their dependencies. Package X requires packages Y and Z plus verison 3 of package Q, meanwhile package K requires version 2 of package Q and doesn't work with version 3. There are package managers that try to simplify managing this, but it's a big problem.
Suppose MS brings out a fancy new filesystem. Is it a pay-for package? What applications will depend on it? Will they work with plain old NTFS, and what happens if MS decide to base future OS features on an optional package?
There's a name for optional components you ad to an operating system, and it's 'applications'. Microsoft's fragmentation of their operating system into half a dozen flavours may look good in a marketing presentation, but in practice it looks like a huge blunder on technical grounds. Unfortunately, the marketeers are in charge over there now and further market experimentation with new sales and support models isn't going to improve things.
I think what they'll do is lower the initial price for Windows but then charge people every year to renew the license, keep getting security updates, etc.
They'll claim it's what their customers want, and that it makes Windows more affordable to people, and who knows, maybe they'll be telling the truth :)
But what it will really be about is continuing to make money off of Windows buyers for years into the future, rather than the big "pop" at the buy and then *nothing* - which forces them to have to always develop the Next Big Thing to keep the money rolling in.
This way, with subscriptions, the money will just KEEP rolling in, year after year, as long as people don't want their Windows to deactivate - they'll kind of have people by the proverbial testes.
The counterpoint to this, of course, is that Microsoft does continue to provide security updates and add-ons some years into the future, so maybe they should be compensated for continuing to do that. Otherwise, why shouldn't they discontinue security updates to Windows 2000 tomorrow?
But really, what it will be is about monetizing all those many, many, many people who get one version of Windows and then never upgrade because 1) they fear change (earnestly), 2) they just don't see the value in upgrading (i.e., what they have is "good enough").
Hmm... Yearly payments to Microsoft to keep your Windows functioning - maybe we can call it the "Microsoft tax".