There are a lot of products that are this consistent, if not moreso. Clothing and cars and big one. Everyone looking to buy a car knows that a new model comes out every year. They know if a model just came out or has been out for 10 months and will be rev'ed shortly. And some people also track when a new design is coming.

But this is less common in consumer electronics. And frankly, this wasn't common until the iPhone. Even iPods didn't get upgraded by consumers much.