Apple Inc.'s stock is still a "Buy" for analysts as Piper Jaffray's Gene Munster remains optimistic in his latest note to the investors.

Munster said the firm is bullish with its low expectations on the iPhone maker's latest product releases, including the long-rumored iWatch and iPhone 6 with a bigger screen.

He added Apple's stock will remain "steady" if new products are deemed "unimpressive." He believed the stock will rally if Apple will launch unexpectedly innovative products.

The analyst noted Apple Inc. will make an announcement about increasing its dividends or a stock repurchase after the company's first quarter of 2014 earnings report. Apple has led U.S. companies in the value of stock buybacks in the past quarter of 2013. Aside from Apple, other tech giants also making huge repurchases of their stocks.

Apple is expected to release its first quarter figures on April 23. Piper Jaffray's price target for Apple is at $640. Munster expects a growth of 5 percent for Apple in year-over-year by June, which is lower compared to the Wall Street's 10 percent projection.

The analyst cited iPhone 6 will have a bigger screen than the current iPhones sold worldwide. This will be Apple's "key selling point" and may drive the stock price higher if investors find it innovative.

Apple stock could increase by 20 percent in 2015. iPhone 6 is set to be rolled out in the summer or fall. Barron's had previously said it is certain that Apple's latest iPhone will have a bigger screen compared to its 4-inch predecessors. A bigger screen iPhone could attract new users and give iPhone owners incentive to upgrade to the latest iPhone.

The ISI Group has upgraded Apple stock to a "strong-buy" rating as the firm has a $600 price objective on the stock. Apple investors may see significant gains in the company's stock in the next 12 months.

According to Pacific Crest Securities Analyst Andy Hargreaves, Apple stock could reach $635 with the impending release of iPhone 6.