Steve Jobs is to make a rare appearance at Worldwide Developer Conference today showcasing the latest Apple brainwaves. But will iPhone 5 be among the goodies revealed?

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The CEO who took medical leave earlier this year following a long battle with cancer will showcase the new iCloud music streaming service as well as iPhone update iOS 5, which it confirmed last week, and one also wonders if Jobs may unveil the long anticipated iPhone 5.

Although the tech giant made no mention of the device to replace the iPhone 4 in its official statement, the iOS 5 update will be revealed to developers so it is still uncertain whether a surprise guest in the form of a new iPhone might make an appearance also.

Here’s what the company did say:

“Apple CEO Steve Jobs will open the company’s annual Worldwide Developers Conference (WWDC) with a keynote address on Monday, June 6 at 10:00am when the he will announce, Lion, the eighth major release of Mac OS X; iOS 5, the next version of Apple’s advanced mobile operating system which powers the iPad, iPhone and iPod touch; and iCloud, Apple’s upcoming cloud services offering.”

However, some analysts believe the iPhone maker may hold off until later in the year to catch the Christmas rush, citing a September date as a possibility.

For its part, the tech giant is said to have penned agreements with some music heavy weights like Universal Music Group, Sony and EMI, according to the LA Times, for its other new kid on the block, iCloud, which Apple is calling a “cloud services offering” and said to offer unlimited music and other content streamed from the sky.

Rivalling Google’s new Beta music streaming offering and Amazon Cloud Player, it will be free to iTunes customers for a period and then users will be subject to a fixed charge of $25 a year, according to sources close to Apple.

Jobs’ attendance, confirmed last week via an Apple press statement, marks a rare appearance for the CEO, whose only recent public attendances have been the iPad 2 launch in March and presidential dinner with Barack Obama earlier this year, where he was said to appear gaunt, so attendees will be hoping his appearance is improved this time round.

Its next-generation desktop operating system, Mac OS X Lion will also be revealed.

Jobs’ keynote address will take place at 10 am San Francisco local time today.