You arent quoting Microsoft. The second part is from Microsoft but the first is not.
Again windows Core OS has not been described from Microsoft as the future of One Core but like I said in my edit its fair to deduce that this is the future of One Core, but Core OS is not built in the same way as One Core. The specifics are different but with a similar goal in mind. One Core required different ways to make it work correctly with the other iterations of One Core.
Where as Core OS will literally be built on the same foundation and the iterated upon.
Future iterations of Windows 10 does not include current Windows 10 because Core OS will not run win32 natively. They will not update legacy Windows 10 to Core OS. If that was the case Windows 10X wouldn't exist.
Yeap... the actual OneCore is build for each platform... it is a different OneCore for each platform (the Windows 10 uses a OneCore build specifically for PC hardware that is a bit different from the OneCore running in Xbox One).
Windows Core OS come to make all platforms to share the same base... so the same Windows Core OS will be running inside Windows 10 or Xbox OS.
It is modular so on Windows 10 you will have the Windows Core OS at base and all the modules to give you every functionality you have today in Windows 10... that means you will for example a Win32 module to run legacy software.
Same applies to Xbox OS... the base will be Windows Core OS and after that it will be build the functionalities (modules) specifics of the Xbox OS.
That is the ideia of Windows Core OS... the same base for all platforms.
Windows 10X is a OS specific for dual-screens... it uses Windows Core OS as base and add modules over it reach it pourpose.
Windows 10 is a OS specific for desktops... it will be upgraded to use Windows Core OS as base plus the modules over it have all the functionalities it has today.
Xbox OS is a OS specific for Xbox consoles... it will be upgraded to Windows Core OS as base plus the modules to make it works best as a gaming console.
Win32 legacy is just a module that can be build over Windows Core OS base... so all platforms that add that module can run Win32 apps.
Windows Central give an example that shows what Windows Core IS is about:
"It's essentially a modular platform. Any feature or function Microsoft builds for it can then be applied to any Windows Core OS device that it wants. For example, let's imagine Microsoft builds out Win32 support as a component for Windows Core OS for desktop and laptop devices. Since that work has now already been done, Microsoft can also bring that Win32 component to HoloLens 2 or Surface Hub 2X running Windows Core OS, enabling that functionality on those experiences too. "
The modules or components build over Windows Core OS base can be added to all platforms if they wish (of course if a platform doesn't need that module it won't be added lol).
That is the biggest advantage over the old model MS was using (where you have to develop the feature like W32 support to every platform you want to have that feature... now you MS develop a modules compatibles with all platforms that uses Windows Core OS).
The ideia of Windows 10 not receiving a big upgrade to use Windows Core OS as base is complete the opposite of what MS is trying to reach with Windows Core OS... it could take time (because Windows 10 is feature extensive and so needs that MS creates all these modules to all these features) but Windows 10 soon or later will receive that upgrade.