Apple is expected to announce a new or updated iPhone at 1 p.m. EST on Tuesday. Those looking for a dramatically new version of the iPhone are likely to be disappointed.

It is expected that tomorrow’s announcement will feature a refreshed iPhone 4 model with under-the-hood enhancements, including a unified chipset that will work across multiple carriers with a significantly faster main processor. An upgraded camera is another possible addition. 

An inadvertent product reference on a beta version of Apple’s iTunes software released this week revealed an “iPhone 4S” as one of the iOS devices the software supports. Apple quickly pulled the beta after Apple rumor sites reported the iTunes product reference

Consumer demand for the current models remains extraordinarily strong, with Apple selling just over 20 million iPhones worldwide in just the second quarter of 2011 alone. Incredibly, both of its current devices are over a year old — the iPhone 3GS was released in 2009 and the iPhone 4 in 2010.

Apple, as it has in the past, may also release a new feature or two that will only work on the new hardware. One such feature is expected to be a voice control capability that will allow complete hands-free operation of the device. Apple last year acquired a Siri, a firm that developed an intelligent voice control application for current iPhones. 

The big story for users of iPods, iPhones, and iPads will be the release of iOS5, the operating system that powers the devices. The new system will work with most late model devices and will connect users to Apple’s iCloud infrastructure for wireless data backup and syncing across iOS devices and computers — reducing or eliminating the need to connect the device to iTunes. The iCloud service will also include an “amnesty” program for those who may have acquired music in the past illegally. A $24.99 fee will give users the ability to match their music library to Apple’s legal collection, providing anytime access to music that was downloaded or purchased elsewhere.