I think their intention is to just release 10.1 10.2 10.3 and so on.
They know consumers don't upgrade anything anymore if it costs money. Windows 7 was good enough for many people they never felt like they needed a new OS. A lot of people still feel that way about Windows XP I believe its market share is still 30%?
As I'm sure everyone here is aware Windows 10 will be a free update for people who own Windows 7 or Windows 8/8.1 licenses. Apple has made their updates free for the past 2 versions I think and the two before that were like $9.99 down form the previous $89 price that they used to charge.
And of course we have Linux where I can't think of a single desktop targeting distribution that charges users money to use it. The world has changed significantly over the past 10 years and Microsoft knows it's a much better idea to charge a minimal fee for the operating system and then make their margins on other things.
Services like Office 365, the Windows Store where they take a 30% cut of all sold software and so on.
Personally I like the idea of major new operating system releases. Especially when they arrive on predetermined schedules. We've all experienced the annoying update of death I'm sure where you've installed a software update only for it to majorly mess things up, now imagine getting an entire operating system refresh that way that changes thousands of system level libraries that your software depends on.
I think it's a bad idea but I'm expecting them to do it as I said at the start of this post, issuing 10.1 in 2016, 10.2 in 2017 and so on with things largely staying the same. It's very much the Apple model as with their operating system it was possible to upgrade from 10.6 all the way to 10.10 (current release) through their version of Windows Update/Windows Store which has been combined in to one application on OS X.
Personally just talking about Windows 10 itself, I've been using the technical previews and it's not bad. It's an improvement over Windows 8 but I still don't feel it eclipses Windows 7. I still find myself longing for the GUI that Windows 7 had with the performance that Windows 8 has. Windows 10 takes what we hated about Windows 8, the Metro start screen, and melds it even further in to the desktop experience and personally I don't like it.
The UI from the Metro apps which by the way I should call them Modern apps as they had to rename them from Metro due to a trademark dispute, just feel very large, encompassing, lumbering. They waste so much space on the screen because they are designed for fingers, I don't own a touch screen on my desktop computer nor am I ever likely to acquire one but these applications don't scale small enough to look correct on a display where you're using a precision finite pointing device; the mouse.
I feel like with Windows 10, which by the way absolutely screams on newer hardware especially SSD's and multi-core systems, takes one step forward but then two steps back.
I can give a great example of this, the control panel. In there you find things like your display settings, background selector, windows update etc in Windows 10 these things have all been stuffed in to a "Modern" UI application called Settings and it just looks bad. Each of these features use very little of the available window space, they give very little information when you use them (Windows update especially is just a barren giant white box) and the UI elements and text sizes are giant. It just looks bad.
I'm hoping Windows 10 will turn in to a release I want to use but honestly it just pushes me more and more towards Linux and Mac OS X which both feel more refined when it comes to the user interface and no matter how fast Windows feels on my hardware if the UI is pissing me off I'm not going to accept it or use it.