iWatch? Larger iPhone 6? What to expect from Apple event.

Apple's big event Tuesday could debut an iWatch and a larger iPhone 6. Here's a guide to what we know and what we think we know.

The rumor mill surrounding new Apple products churns once again this September. Each fall, the company trots out a new phone and upgraded features. But what should we expect this year? The iPhone is expected to get an upgrade and a newer, larger size. Apple will likely release iOS 8 to the public (a beta version was available to developers since it was unveiled at the Apple Worldwide Developers Conference in June). A wearable device, unofficially dubbed the “iWatch,” might be making an appearance at the keynote, which takes place on September 9.

In anticipation of these announcements, here are a few features we’re expecting to drop.

iPhone 6

Larger iPhone screen size – Apple is expected to beef up the iPhone’s screen size to 4.7 and potentially 5.5 inches. (The current iPhone has a 4-inch screen.) The 4.7-inch version could make an appearance Tuesday, but it’s possible the 5.5-inch version may be announced later, according to reports, which suggest the larger size has hit supply-chain troubles.

Sapphire crystal screen – In addition to size, Apple may also improve the materials for their screens. According to The Wall Street Journal, Apple is betting $700 million on factory-made sapphire crystal to replace the current glass screens. Apple already uses sapphire crystal for the iPhone 5S camera lens and Touch ID button.

Reversible USB cable – The new USB cable supplied with every iPhone will reportedly be reversible. No more guessing which way the head should go when you plug it into a computer or into the wall adapters.

Mobile payments – Apple signed an agreements with Visa, MasterCard, and American Express to enable wireless, mobile payments. This is done through "near field communication" (NFC), which allows smart phones to establish short-range radio communications that can perform a wide range of functions, such as authorizing a card transaction (in this case) or unlocking a door. Google has had NFC payments for a while on its own Nexus 4 and Google Wallet service.

Faster processor and better battery life – The iPhone 6 (if that is the official name) will likely sport a higher capacity battery than its predecessors – up to 46 percent higher capacity compared to the 5S, according to reports from Apple Insider. The processor will also likely be upgraded, for quicker response time and graphics rendering.

iWatch

Many expect a so-called iWatch, Apple’s break into the wearables market. The iWatch could to pair with iOS’ upcoming Health app, which tracks an individual's health and fitness metrics. Rumors point to the iWatch being announced at the Sept. 9 event, though it may release as late as next year.

iOS 8

Revamped keyboard - iOS’ keyboard will show a predictive-keywords bar above the keyboard. iOS 8 will also finally bring third-party keyboard support, bringing in a whole suite of customizable keyboard apps that were, until now, unavailable on Apple mobile devices.

Family sharing - Digital purchases of apps, music, and books will be sharable to six other family members without sharing an Apple ID.

iCloud documents - Apple’s iCloud will have increased functionality, bringing the cloud service closer to competitors like Dropbox and Google Drive.

We'll discover the truth when Apple reps take the stage on Sept. 9.