Also, just for reference, all of the Windows 10 main version numbers, e.g, 1511, 1607, and 1703, are the YYMM of their release (or close to it, some were delayed a couple of weeks)
This article on blog.juriba.com does the best job I've ever seen of describing the Windows 10 branching timeline both for the versions already out (and 1507 - the original release, is already out of support) and the next two upcoming ones. This graphic they use:
is the best visual representation of the continuous roll out model of the ongoing versions of Windows 10 I've ever seen. While Windows 10 "current version," whatever that version happens to be as time goes by, is supported until the end of life dates Microsoft has published for Windows 10, any version that has been superseded is not, and those versions are generally supported for approximately 18 months from date of release. Since everyone is expected to be continuously updating to the latest version this is exactly what should be expected.
There is, however, already one exception to that rule with the recent announcement regarding Atom Cloverleaf (I think it's Cloverleaf, it may be Clover something else) processors. Unless Intel releases some tweaks these will not be able to use any version of Windows 10 beyond Version 1607 (Anniversary Update). Microsoft has already announced that they will continue to provide security updates on Version 1607 for those with these processors through the end of support date for Windows 8.1 in January 2023, since all of these machines running Windows 10 would have been part of the free upgrade process. I fully expect to see this sort of thing occur again for relatively recent processors that had relatively short production lifespans that came out during the Windows 8/8.1 era. We shall see.
Brian AKA Bri the Tech Guy (website in my user profile) - Windows 10 Home, 64-Bit, Version 1809, Build 17763
Travel is fatal to prejudice, bigotry, and narrow-mindedness, and many of our people need it sorely on these accounts. Broad, wholesome, charitable views of men and things cannot be acquired by vegetating in one little corner of the earth all one's lifetime.
~ Mark Twain