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.