What's in store for the next iPhone? (John Moore/Getty Images)

It's only a matter of weeks before Apple is expected to lift the curtain on the next version of the  iPhone.

Apple has not actually confirmed it's launching a new iPhone, but analysts think the phone will have a larger screen and may come in two models. One is expected to have a 4.7-inch screen, while the other could be as large as 5.5 inches. Apple has lagged behind competitors such as Samsung in offering these larger screen sizes, which have become more popular as people watch more streaming video on their phones.

A recent message, since deleted, from the micro-blogging account of Chinese carrier China Telecom appeared to leak an image of the "iPhone 6," although CNET later reported that this appears to have been concept art.  The image showed an iPhone with rounded edges similar to the iPad Air that Apple released in 2013, according to a report from Sina News. The ad in the Sina News article carries the tagline "Even Better."

Some have also wondered whether the iPhone will be more expensive for consumers. An article from the Huffington Post on Monday raised the specter of a more expensive iPhone, citing an April analyst note and a TechRadar report based on anonymous leaks from Apple's supply chain, that the phone could cost as much as $299 with a two-year contract. That would be far more than its traditional $199 price. And the phone would be even more expensive off-contract; a new iPhone 5s currently starts $649 without a plan.

Apple did not immediately respond to a request for comment.

It's a hard claim to evaluate. Increasing the size of the screen would logically add to Apple's expenses. But a price increase could also hurt the company in its competition with Samsung and other phone makers who offer phones with bigger screen sizes at iPhone prices. Given the competition, Apple has a strong incentive to keep with its traditional pricing if it can -- even it means cutting into the amount Apple makes off of each iPhone.

The iPhone is particularly important to Apple, because it makes up the bulk of its sales, as you can see here.

Last week, Morgan Stanley analyst Katy Huberty noted that demand for the next iPhone or iPhones is poised to be unusually high, even for Apple. "Over half of the iPhones in use are due for an upgrade," she wrote in a report for investors last week, a copy of which was obtained by The Post. She estimates that Apple could take "11 points of market share" with its larger screen sizes, due to demand from Apple fans. Apple currently has 35.1 percent of the smartphone market, according to the latest figures from the IDC research group. Samsung currently leads the world's smartphone market, with 25.2 percent of the market.

Before you consider upgrading, though, it may be worth noting that on Saturday, the company put up a service page saying that iPhone 5 models sold between September 2012 and January 2013 may have battery life issues, and that many models were eligible for a free battery replacement.

To find out if your phone qualifies, you can head to Apple's Web site and plug in the serial number from your phone. To find that, head to the Settings app on your iPhone, and go to the "General" menu. From there, tap on the "About" screen, and you should see your serial number listed somewhere within that menu.

How to find your iPhone serial number. (Screenshots by Hayley Tsukayama)