thats where you're wrong. I'm not saying that they will break records always, but it's definitely not impossible - because apple is in the business of selling consumables. something that lasts 2 years before it needs to be replaced again. the record breaking crowd of two years ago will potentially be a record breaking crowd this year. they're not going to suddenly stop using a cellphone.
As long as apple can keep their customers happy and give them zero incentive to jump ship to another platform, and in the process attract more customers from android, as well as emerging markets, like china and india, thereby making the pie bigger, they make it possible for themselves to keep breaking records.
Don't be fooled, you're not apple's customer that bought a $750 iPhone, you're apple's customer that buys a $750 iPhone every two years, forever. you help break apple's record not just last year, but every two years from now on.