This is a surprisingly thought-provoking comment and the theory checks out.

Until Apple are able to break out of this mould I feel they'll be stuck at this combination of

a) uninteresting yearly iterations

b) ever increasing base phone prices for little end user gain

I don't thinkt hey're able to paint themselves out of this corner on the smartphone front.

They have iOS as a decent but certainly not impregnable moat for iPhone. Some brand new groundbreaking product will be needed very soon to prevent the Apple stock price from steadily declining. (It already starting plateauing 15 months ago.)