I went ahead and moved your thread, since it's not an Apple Rumor or Report.
As to your question - Apple's sales ebb and flow like any company's. This last quarter was one of the first where year-over-year growth wasn't as strong as it's been in several categories. I think some of that is to be expected, especially when practically the entire Mac lineup has been stagnant in terms of significant design changes. As far as their best days being behind them... hard to say. We never know what's in the works or how consumer tastes will shift.
One thing is certain, however... Apple is sitting pretty on a mountain of cash. They are diversified in terms of their business model, with quite a few revenue streams. In the markets they compete in, their products are easily the most profitable (by a long-shot). This is not the Apple of the 1980s. They are a money-making machine, and short of an unforeseen worldwide catastrophe, they will continue to be so for decades to come.