A mac only framework doesn't sound like an election killer at all considering windows still has a huge user base.
Things like flutter/react are completely going to devour the platform specific space for everything except usecases that require specific hardware(which apple is also losing because they're ignoring scientific/gaming marketshare by cold-shouldering nvidia,ML and AAA game devs in general).
i think apple is trying to "hunker down" until internet speeds improve enough that everyone is using a streaming service for all the hardware intensive stuff and they can continue selling pretty thin clients like ipads/iphones/iARGlasses