London, KY is obviously not a 'substitue' for London England. However, if housing differentials become too significant, other large US cities (like Chicago, Seattle, etc) become very viable alternatives to SF. The job markets and amenities are similar.
If you really think 11% in SF is sustainable, and that a lower rate will occur in other large cities then the 50% assumed housing premium you currently pay in SF will rise to 6X. In my experience, salaries do not very that much among these locations for similar jobs, so the question is whether someone will pay a 600% premium to live in SF as opposed to another of these large cities (despite making the same money). I say no. If you believe 11% will occur in SF, the only alternative to this significant price differential is similarly huge increases for other areas as well.
So if you think 11% is sustainable for SF which is it?
a) people pay a 600% premium to live in SF relative to other large cities like Chi and Sea (despite similar salaries)
b) other large cities RE will appreciate at a similar rate
I really don't think there's an option 'c'.
ps - I wouldn't necessarily make a similar argument for Honolulu. There are enough differences between HI and mainland cities that I'm not sure they are viable alternatives. Maybe you'll see 11% there... but I still doubt it.