Instead it will be an ongoing rolling release of incremental changes.
I genuinely don't understand this move by Microsoft. Of all the things you want to be stable and reliable over time, your basic OS and platform software has to be at the top of the list.
While dumping any responsibility to support software older than the latest release has obvious appeal for developers, evergreen software has mostly proven to be mediocre-to-disastrous from the user's point of view so far. For business users, it's also painful from an internal support point of view, for much the same reasons. And as you mentioned, for an OS or other platform software, anyone developing other software that runs on top of it also faces problems.
About the only thing this kind of constantly updating deployment model has been good for is getting security and stability patches out faster. This is beneficial, but that benefit is tempered by the "just ship junk and patch it later" philosophy that has become widespread at the same time. Many of those patches simply shouldn't ever have been necessary in the first place, but new releases are now routinely of such poor quality that many people just don't bother, and advice to wait until SP1 or the equivalent is common.
If I were Microsoft, I think I'd want my new flagship OS to be the stable, reliable, trustworthy antidote to Apple's broken-within-a-week operating systems[1], not something with the same reputation for constantly tweaking things as Chrome/Firefox, on-line SaaS apps, and the like.
[1] For legal reasons, I would like to point out that not all Apple operating systems break within a week. In fact, the fastest I have seen a mainstream Apple device break in practice was approximately an hour after purchase, when iOS updated on a mobile device almost immediately, leaving the device so much worse than what the purchaser had previously tried out and thought they were buying that they took it straight back to the shop and demanded a full refund.
Businesses have had the ability to manage update deployments for a while now. Big Win10 feature changes will likely come in a service pack form or similar, with security fixes and minor updates using the same model they always have.
A business will typically test and verify updates before pushing then out to their employees.
Businesses which allow its users to perform updates directly from Microsoft already face the issues you describe. (Many updates can and have caused issues. Especially the occasional broken patch that gets rolled back shortly after release).
I can certainly see this being an issue for support companies. On the other hand, they will likely still have some form of versioning to base their support on. "Sir, please do XXX. You should see something saying Windows 10 Service Pack and then a number. Can you please tell me what that number is?"
Businesses have had the ability to manage update deployments for a while now.
Sure, but someone still has to test each update as it applies to each critical system or widely used standard PC configuration before giving the OK to roll it out across the organisation. If MS moved to releasing non-essential updates in an ad-hoc fashion, it seems inevitable that the result would be either a scheduling and resource management headache for corporate IT departments or (perhaps more likely) a general policy of not deploying non-essential updates at all by default in large organisations because the hassle of keeping up isn't justified. Corporate IT have enough to worry about already without someone potentially moving the goalposts on a daily basis.
I still don't see how what you are describing is any more or less of a headache than supporting Windows XP a decade after the first release.. it's still rolling updates, just with less intensive UI changes over that period.
The same goes for companies supporting Windows 7 today... they're using their own base, with cherry picked updates. It seems to me, that this would be easier to manage, than keeping up with rolling from xp/7/8/8.x etc.
I genuinely don't understand this move by Microsoft. Of all the things you want to be stable and reliable over time, your basic OS and platform software has to be at the top of the list.
While dumping any responsibility to support software older than the latest release has obvious appeal for developers, evergreen software has mostly proven to be mediocre-to-disastrous from the user's point of view so far. For business users, it's also painful from an internal support point of view, for much the same reasons. And as you mentioned, for an OS or other platform software, anyone developing other software that runs on top of it also faces problems.
About the only thing this kind of constantly updating deployment model has been good for is getting security and stability patches out faster. This is beneficial, but that benefit is tempered by the "just ship junk and patch it later" philosophy that has become widespread at the same time. Many of those patches simply shouldn't ever have been necessary in the first place, but new releases are now routinely of such poor quality that many people just don't bother, and advice to wait until SP1 or the equivalent is common.
If I were Microsoft, I think I'd want my new flagship OS to be the stable, reliable, trustworthy antidote to Apple's broken-within-a-week operating systems[1], not something with the same reputation for constantly tweaking things as Chrome/Firefox, on-line SaaS apps, and the like.
[1] For legal reasons, I would like to point out that not all Apple operating systems break within a week. In fact, the fastest I have seen a mainstream Apple device break in practice was approximately an hour after purchase, when iOS updated on a mobile device almost immediately, leaving the device so much worse than what the purchaser had previously tried out and thought they were buying that they took it straight back to the shop and demanded a full refund.