"It's unlikely that dumb-phone holdouts are going to go straight to a top-of-the-range smartphone"
Why? That's exactly what I did when I finally got a smartphone two years ago. My logic was simple: I wanted to buy a phone that could handle anything that might come along during the lifetime of the device.
The surveys showing greater brand loyalty among Apple owners are false, though - in my experience, at least. I see people saying "I think this is where I switch from my iPhone to Phone X" all the time, but I haven't once seen someone say "I'm disappointed in my Galaxy SIII, I'm going to buy an iPhone".