Pros bet Apple event will rocket shares higher

Barring company executives and a few employees, nobody knows exactly what Apple will unveil at its media event scheduled for Sept. 9. But that hasn't stopped Apple observers from speculating.

Many think the technology giant will reveal the new iPhone 6 with both 4.7-inch and 5.5-inch screens—bigger than the 4-inch screen on the iPhone 5s and 5c.

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Such a product would allow Apple's stock to finally break from its "pretty consistent trading pattern" of rising ahead of the announcement, only to tumble in the months following the release, Dan Niles, founding partner at Alpha One Capital Partners, told CNBC on Monday.

"This one, I think, has the potential to be different … This, in my opinion, is the best product that they've had since really the 4 or the 4s, which is when they introduced the two cameras on the phone; the front and the rear-facing," Niles, an Apple shareholder, said on "Squawk Alley." "I think that will drive a big upgrade cycle because you're going to get a fatter, wider phone. I mean, I haven't upgraded for three years and I think there's a lot of other people who have been waiting for a compelling reason to move. I think this will give it."

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Steve Milunovich, managing director at UBS, also noticed the pattern of Apple's stock selling off after a product announcement. Shares fell when the company had unveiled the iPad and later the iPhone 5 to a weak reception, he noted.

But "this time is different," Milunovich said last week on "Squawk Alley."

Between the possibility of the latest iPhone and even an iWatch, Milunovich maintains a "buy" rating on the stock and thinks it could go to $115 a share, roughly a 15 percent premium from current levels.

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"The new phones are going to be addressing a third of the market that Apple does not address today," Milunovich said. "They've not played in in larger screen phones, suggesting you could have a very strong upgrade cycle that we still think could be more people expect."

Milunovich has "relatively conservative expectations" for the iWatch because he thinks the iPhone will be "the main event." Still, he noted most analysts have not factored the iWatch into their price target models.

Jean-Louis Gassée, former president of Apple's product division, wouldn't speculate on what Apple might announce. He did, however, say an iWatch is unlikely to "move the needle."

"They have one and only one business: personal computers," Gassée told "Squawk Alley" on Tuesday. "These come in three sizes: small, medium and large; smartphones, tablets, and PCs—desktops and laptops—and everything else supports that business in an ecosystem."

The "sweet spot" for Apple is the balance between PC and tablet devices, Gassée said.

—By CNBC's Drew Sandholm. Reuters contributed to this report.