Comment 1)
It is not uncommon in software versioning to see things like:
10.9
10.10
10.11
...
10.20
(10.10 != 10.1) && (10.20 != 10.2) for software versioning
we also see things like
10.9.1, 10.9.2 ... 10.9.10, etc...
Version numbers are not decimal numbers the are representative of the software.
A.B.C....
A = Product Version, usually meaning the core of the product was significantly altered or even completely replaced (think Mac OS 9 to Mac OS X). "A" can be any integer number.
B = Secondary level change, ("Major" Product Revision) In the case of Mac OS X it is used to signify a new Major Release of Mac OS X. Feature updates, core (i.e. Kernel) enhancements, etc... "B" can be any integer number.
C = Tertiary level changes, ("Minor" Product Revision) Usually for large updates to the Major release. For comparison sake could be similar to a "Service Pack" in MS/Windows terminology. Bug fixes, refinements, may have some functionality/feature enhancements. Often they include all the security/bug fixes that were released since the prior Tertiary level changers were released. "C" can be any integer number.
Technically they could continue on down with more levels .D.E.F.G, etc... but they typically don't bother getting that granular. "All levels" can be any integer number.
The point is, this isn't standard numbering. Like the Duey Decimal System, it gets more granular as you go down the line, but unlike the Duey decimal system you are distinguishing each level with a "dot", and the number between each "dot" counts up independently and is its own number. any whole number 0-∞ is technically allowed.
Comment 2 and back on topic:
The design in the article has some aspects I like, but it does "feel" to much like Windows for my taste.
https://www.behance.net/gallery/The-next-Mac-OS/9995849
Also is good, but could use some refinement.
In both cases I do like seeing a bit more translucency. for example if Notification center slid on top of the desktop with a translucent background I would personally like that.