Barclays Capital analyst Ben Reitzes told clients Tuesday that a new iPhone form factor is the, "real key to [AAPL] shares in 2010. In a research note obtained by The Mac Observer, Mr. Reitzes said that he still expects Apple to announce a tablet on January 27th and that Mac sales are still on the rise, but that a new iPhone update later in the year will be the real factor in moving the company's stock this year.

"While we are upbeat about the possibility of a tablet and acknowledge the incremental impact of a tablet device to our model," the analyst wrote, "we are growing even more enthusiastic about the iPhone's potential upgrade cycle this summer, which could last longer than usual -- well into FY11 when Verizon could come aboard in the U.S."

The analyst didn't elaborate on what kinds of changes Apple might bring to the iPhone, and he maintained his price target of US$260 per share, with an overweight rating on the stock.

Shares traded lower in late afternoon trading Wednesday, giving back some of the gains booked Tuesday on the heels of Apple's announcement of the January 27th media event. As of this writing, the stock traded at $211.87, down 3.17 (-1.47%), on strong volume.

*In the interest of full disclosure, the author holds a small share in AAPL stock that was not an influence in the creation of this article.