In an open letter sent to Apple's board, bllionaire activist-investor Carl said Apple's shares could double in value and urged the company's board to buy back more shares using its cash pile. "We believe Apple is dramatically undervalued in today's market, and the more shares repurchased now, the more each remaining shareholder will benefit ...," Icahn said in a letter to Apple's board. "Therefore, given the persistently excessive liquidity of $133 billion net cash on Apple's balance sheet, we ask you to present to the rest of the Board our request for the company to make a tender offer, which would meaningfully accelerate and increase the magnitude of share repurchases," he added.

Icahn, who pledged to keep his own stock out of any repurchase, said Apple stock should be trading at $203.

Icahn said Apple was poised to take market share from Google's Android platform in the premium device market.

Icahn has in the past urged Apple to return more of its cash to shareholders and pressured the company to increase its stock buyback program and raise its dividend.

he also praised the significantly upgraded iPhone 6 and iPhone 6+, which feature larger screens, the capability to make mobile payments, and improved specifications, noting that he believed the phones would take market share in the premium category. He compared the iPhone and Galaxy S5 dynamic to a choice between a Mercedes and a Volkswagon -- at roughly the same price.

Icahn also weighed in on Apple's various businesses, including the Apple Watch. The investor believes the smartwatch "will have a significant impact on Apple's growth" over the next three years. He also said he believes that Apple will release an UltraHD television set in fiscal 2016, although he acknowledged that it may never happen.