To disrupt Apple, a rival would have to introduce a better user experience across computer, mobile and TV platforms at a lower price, Garcha said.
As for international growth, Apple stands to generate another $90 billion to $95 billion in the next five years if it can replicate its success in China among consumers who can spend an average of $600 a year on Apple products, according to Credit Suisse.
To do that, Apple needs to extend its reach in markets like India, Brazil and Russia, where it currently lacks direct retail presence and local support, Garcha said.
Gene Munster, senior research analyst at Piper Jaffray, said the iPhone differs from the iPad — a product that has seen sales decline for two years — because people use handsets more frequently. The iPad benefited from pent-up demand when it was released, but that demand has now been satisfied and has died off, he said.
After nine years of following the iPhone, analysts have a good handle on how the next cycle will play out, Munster said.
"This next wave of people that are upgrading, this echo effect from the iPhone 6, is about 30 percent bigger than the iPhone 6s," he told CNBC's "Squawk Alley" on Tuesday.
Disclosure: Credit Suisse makes a market in the securities of Apple and has managed or co-managed a public offering of securities for Apple within the last 12 months.