I certainly agree that their growth will first fall off and be flatter. And yes, predicting the bust isn't easy (or more of us would be rich). Generally from what I've observed, the faster a business grows, the faster it can fall if things don't go as planned. Netflix is a recent poster child. Apple's a different company of course, but their insane market share can only go down from here due to competition making inroads. Android is no small potatoes in this game.
The most telling thing in the near term is what their next break-through product will be (what Jobs would deem "magical"). I don't see anything very promising. AppleTV or siblings? Watch out if they pour their resources into that as all I see is a big money pit. They've proved me wrong before so we'll just have to see. I honestly wouldn't be surprised to see their stock plummet into the 200's or less in the not-too-distant future.