The iPhone will be replaced by a newer iPhone. It's not going anywhere. The title comparing it to a Polaroid or a Walkman is silly. Those devices did one thing.
Ford has been making the F-series pickup truck since 1948. Apple can expect the iPhone to enjoy the same run.
Think you’re right about iPhone, and Androids from Samsung and Motorola. Until a disruptive / significant unmatched feature, function or price point comes along these brands and their devices will be around a while.
What I think could be changing is consumer attitude and preference for flagship level devices. This could be evident in the results of the latest Apple release. Perhaps consumers are not as willing to drop $900 or more annually and/or do not perceive sufficient incremental value to go from i8 to i9, etc. There’s great devices from top manufacturers between $3-600, perhaps consumers are also starting to more closely weigh these devices to flagships also.