in that case you can look at the last series of years of WWDC with apple driving swift for developers, and swift's adoption by apple by increasing amounts of the OS. Which seems like the equivalent, only not in blog form.

Not terribly familiar with Swift but my understanding was it was more an app programming language. Is Swift suitable for writing OS code?

Swift is a very powerful and robust language. I would expect that they keep going further down the stack with it but the problem will always be, "is it worth investing in a language refactoring on an existing codebase?". I presume all but the lowest level (or server-side) new code is in Swift at Apple nowadays.

Yes, that is even mentioned on its official documentation, a replacement for C, Objective-C and C++.