MS is ahead of Apple in this race to security via taking back control from the end user. I'm with you in theory, but really doubt that on either platform there won't be at least a dev-only way of running arbitrary unsigned apps.

Time will tell. I think it will really come down to the severity of malware problems of the future.

But I really think we'll just move 100% into bifurcated systems (we're already there with Intel's ME to a large extent) where the place that arbitrary code can run is completely segmented off from trusted code.