Swift evolution and governance is open and publicly documented. It will always be dominated by Apple engineers, but the evolution of the language is largely orthogonal to Apple's OS releases.
I'm not sure how much of the standard library is available on the server side.
However, I it's more about the engineers' interest than it is Apple's, and in that respect, the Swift ecosystem has been evolving constantly, e.g., the Swift toolchain was entirely divested from Xcode a month ago.
I can't speak for the .NET ecosystem, but your fears are unfounded. Whether Swift is useful in a cross-platform context is another question, however.
I'm not sure how much of the standard library is available on the server side. However, I it's more about the engineers' interest than it is Apple's, and in that respect, the Swift ecosystem has been evolving constantly, e.g., the Swift toolchain was entirely divested from Xcode a month ago.
I can't speak for the .NET ecosystem, but your fears are unfounded. Whether Swift is useful in a cross-platform context is another question, however.