Shares of Apple (NASDAQ:AAPL) have been on the up and up lately and for good reason.

Apple defied its many skeptics when it reported its best earnings release in recent memory late last month, sending its shares up some 15% in the last month alone. As we shift our focus to Apple's coming product launches in the months ahead, renewed faith from investors is all the more likely to push Apple stock higher.

Although it probably won't need the help in my eyes, Apple recently got another major endorsement from none other than its old frenemy Carl Icahn.

Icahn doubles down on Apple

Carl Icahn is best known for his highly public, and highly profitable, activist campaigns, which have increasingly targeted tech giants like eBay, the now-private Dell, and even Apple in the past several years.

Apple originally entered Icahn's investment crosshairs last August, when the investing legend created a media firestorm when he announced his initial stake in Apple via Twitter.

In the months that followed, the billionaire investor attempted to install a proposed $150 billion share buyback program via proxy campaign, which eventually ended with Icahn throwing in the towel earlier this year. However, Icahn has remained a net buyer of Apple's shares even after ending his proxy campaign.

In his firm's most recently disclosed 13F filing, Icahn apparently increased his stake in the tech giant during the first quarter. All told, Icahn increased his position in Apple by 2.8 million shares during the first quarter, giving him a total holding of Apple stock of 7.5 million shares through the end of March. In terms of dollar figures, this values Icahn's total stake at roughly $4.4 billion.

What's less clear is whether Icahn has acquired more Apple shares in the interim or liquidated some or all of his holdings as Apple's stock has risen lately. So while we don't know for certain, I for one will argue that Icahn would be wise to hang onto his Apple position as the months ahead could provide an even bigger boost to the world's largest publicly traded company.

Big things ahead for Apple

The possible catalysts for Apple in the months ahead are almost too many to enumerate.

For starters there's the increased bullishness and fanfare surrounding Apple's coming existing product launches that should include the highly anticipated iPhone 6 and some kind of iPad refresh as well, both of which could send Apple shares higher.

Beyond the "known" products, there's also the litany of rumored potential products that Apple could introduce at some point this year. Apple CEO Tim Cook has consistently relayed to investors that the company will introduce at least one new product category this year with the top contenders at the moment being an iWatch (my personal bet), some kind of advanced mobile payments platform, or even the supercharged version of its current Apple TV set-top box offering. Any of these moves would create a fresh revenue stream for Apple and help eliminate some of the growth concerns that have proven a headwind to Apple's stock price over the past two years.

Lastly, there are also the economic effects that Apple's recently reloaded stock buyback and its coming stock split could have on Apple's share price performance. Apple's use of its stock repurchase program has proven highly accretive thus far for investors. Even with shares having risen substantially in last past months, there's clearly a fair argument to be made that Apple remains undervalued around the $600 share price level. Beyond that, Apple's coming 7:1 stock split could open the door for Apple's entry into the Dow Jones Industrial Average, a move which would preempt massive buying from both index fund and mutual fund communities.

In Icahn we trust

Icahn has an undisputable track record of investing success, albeit through some questionable tactics at times. Regardless, he tends to get things right more often than not, and his recent buying of Apple's stock certainly suggests that investors might be well served in considering snapping up some Apple shares of their own.

More broadly, as I've hopefully demonstrated above, there are still plenty of reasons for investors to be bullish on Apple's stock throughout the rest of the year even without the Icahn storyline. So while every investor needs to make his or her own decisions and no stock is right for everyone, there are still plenty of reasons to like Apple's stock even after its recent run-up.