Apple (AAPL) has laid to rest fears that sales of its iPhone and other gadgets would top out, Citi's director of investment research told CNBC on Wednesday, a day after Apple posted a record $18 billion in quarterly profit . The company sold almost 9 million more iPhones than expected, while its cash pile ballooned to the point that it could buy about 480 of the S&P 500 (CME:Index and Options Market: .INX) companies outright. "In fact we saw that they actually beat expectations by over 10 to 13 percent based upon sales, units and earnings, and we are seeing it start to break out," Jim Suva said in a "Squawk on the Street" interview.

Read More Cramer: Don't trade Apple-own it Despite a stock runup of 40 percent last year, shares of Apple remain cheap, he said, noting that the stock is trading at 10 times earnings, excluding its hoard of cash.

Apple shares surged Wednesday, up more than 7½ percent to $117.38 a share in midday trading. The company's results were so strong that they added 110 basis points to the S&P 500's earnings growth this quarter, according to Thomson Reuters.

Brian Blair, managing director at Rosenblatt Securities, rates Apple as a buy because he thinks the next quarter will also be strong. While he does not expect Apple's profits to match the fiscal first quarter, he sees analysts once again underestimating the results. He would start to get nervous about Apple's stock price would exceed $130 a share.

Suva also expects some seasonal softening in the next quarter, but noted that the lunar New Year holiday should provide a tailwind as gift giving picks up in Asia. Apple's blockbuster earnings were driven in part by a 70 percent increase in iPhone sales in China. The company sold roughly 10 iPhones every second around the world during the last quarter.

Read More Apple's growth in China: As good as it gets? Handset makers should expect to see their market share in China shrink as the iPhone's popularity grows even bigger there, Blair told CNBC's "Squawk Box." Strong performance from Apple "will continue to some degree for the rest of the year, but that share will come from somewhere, and it needs to come from Android, who holds the market," he added, referring to rival Google (GOOGL)'s mobile operating system. Whether the previous quarter's incredible growth can be attributed to existing iPhone users upgrading their handsets or market share gains at the expense of Android is an important distinction, Nomura analyst Stuart Jeffrey told "Squawk Alley." If the latter is true, Apple can sustain that growth over several years, he said.

Read More Apple to return $200 billion to holders: Analyst The next big question comes for Apple in the fall, when investors will get a sense for how saturated the market has become with the iPhone 6, Blair said. He noted that Apple CEO Tim Cook has said that only a fraction of the company's iPhone users has upgraded to the larger handset. "So a lot of the buyers are new. They're coming from Android," Blair said. In the longer term, Apple faces what Blair called "the law of large numbers." Apple's sales of 74.5 million iPhones in the past quarter are approaching the upper limits that former market leader Nokia reached. The difference is that Apple is selling higher-quality phones, which may lead buyers to hold on to them for longer before upgrading, he said. Opportunities exist for Apple in countries where smartphone penetration remains low, he said. He pointed to India, which has 900 million wireless subscribers, most of whom are still on feature phones. "There are still a few geographies around the world, Latin America included, where Apple can see some growth," he said. He conceded that the company is getting to the point where investors can make an argument that it is heading for slower growth. Citi's Suva noted that the larger format iPhone 6 and iPhone 6 Plus appear to be cannibalizing sales of the iPad Mini but said the blowout handset sales trump the dip in tablets. Sales of the iPad hit 21.4 million units versus a 22.2 million unit estimate.

The key driver for improved iPad sales would be features such as improved multitasking tools that would make the device more attractive to enterprise users, Jeffrey said. "At the moment it feels like its a great couch-surfing tool still. It's a great typing device." Read More Apple Watch shipping in April Cook announced during a conference call on Tuesday that the Apple Watch will launch in April. The rise of the iPad following an initial period of consumer apathy could provide a blueprint for the smartwatch, Jeffrey said.

"Intuitively I'd say the Apple Watch probably takes a long time to really build significant scale, a few generations. But the iPad shows that if people get excited they can buy into these things earlier than perhaps they should," he said.The danger is that consumers see little reason to upgrade once they do purchase an Apple Watch, as they have with the iPad, he added. The next product segment for Apple after its smartwatch launches will likely be a television in 2017 or 2018, he said.