Apple is widely expected on Tuesday to unveil its next-generation iPhone at a news conference at its Cupertino, Calif. headquarters. Before the event begins at 1 p.m. Eastern time, here's a look at upcoming storylines from Apple's big day.

Meet your new host, Tim Cook. For the first time, Apple founder Steve Jobs won't be curating the company's big product announcement. Instead, hosting duties will go to current Apple CEO Tim Cook.

Will Steve Jobs show up? Since stepping down as CEO on Aug. 24 for medical reasons, Jobs hasn't made any public appearances and nobody knows if he'll resurface at Apple's big event.

Apple will talk iPhone. Will it have a larger display, or an implanted NFC chip? Will there be a better camera, or a voice-activated personal assistant? How much will it cost? When will it be released? These questions and others are expected to be finally answered.

iPhone 5 or 4S? It's unclear as to whether the company will debut one or two brand-new phones, or one brand-new iPhone 5 and a slightly-upgraded iPhone 4.

iPhone extending to other carriers. Sprint made a lot of noise Monday by investing $20 billion into Apple's new smartphone, fueling speculation the company must be prepping a big announcement. AT&T and Verizon already carry Apple's iPhone, but landing Sprint would be a big coup.

iOS 5 and iCloud. Apple announced its new mobile platform iOS 5 and its new cloud-based back-up service iCloud in June, and the company said both products are coming this fall. Well, fall's finally here, and Apple's next-generation phone, whatever it is, is expected to have iOS 5 preloaded. Therefore, if Apple announces an iPhone, Apple must also announce iOS 5. iCloud, which allows users to back up and sync their phones wirelessly, is a key feature of iOS 5.

The fate of the iPod. On the 10th anniversary of the iPod, several media outlets have reported Apple will axe two of its oldest music players, the iPod Classic and the iPod Shuffle. If either product is discontinued, Apple may announce an upgraded iPod Touch or a brand-new iPod.

Facebook announcements. Facebook is expected to take the stage to announce its first iPad app, as well as a revamped iPhone app and the mobile application platform codenamed Project Spartan. The new iPhone app will likely feature the new Timeline profiles, which debuted at San Francisco's f8 developer conference in September.

Twitter partnership. Twitter integration is a key feature in iOS 5, and subsequently, it'll be a big topic for the iPhone. No word yet if Twitter co-founders Jack Dorsey and Biz Stone plan to attend Apple's event.

Mystery product? It's completely possible that Apple will surprise us with a product we've never seen before. This wouldn't be the first time. Apple employees had no idea the iPod was even being developed when it was officially announced in October 2001.

So far, Apple has sold more than 110 million iPhones globally.