Thinking further, I wonder if this could be done without any language changes, simply by noting:
class SomeClass {
static let myValue: MyType = ...
}
If MyType is a reference type, in the absence of "class GC" (easy, since we don't do GC), then myValue is clearly an immortal object. If the ARC runtime already supports marking certain objects as not requiring thread-safe reference counting (having some kind of "immortal flag"), then such marking could surely be easily applied to static reference-typed definitions using 'let'.
I see immortality is also discussed in Swift Performance - #39 by anandabits, but it doesn't look to have gone any further.