Analyst Gene Munster of Piper Jaffray has released a report to clients today looking forward to the release of Mac OS X Leopard and potential releases at Macworld.

Munster noted that Apple was “on track” to ship Leopard by the end of October, and predicted that its release could cause Apple’s calendar fourth quarter results to surge by $240 million.

Looking back to the release of Mac OS X Tiger back in April 2005, Munster wrote that 15 percent of Mac users purchased Tiger or a Mac with Tiger pre-installed within six weeks of the launch. In 2005 OS X’s overall user base stood around 12 million users, it is now predicted to be 23 million.

“While we do not believe many consumers delay the purchase of a Mac because of Leopard, we expect its new features and updated look to be positive for Mac sales,” the analyst wrote.

Looking at unit shipments Munster believes that Apple has shipped somewhere between 2 and 2.1 million iMacs and iPod and iPhone sales are likely to be strong.

Finally the analyst added that Apple was unlikely to remain stagnant following the holiday season and said that the Cupertino company was “likely” to expand its portable device range with at least one new system at Macworld 2008. Either a new Mac “subnotebook” or multi-touch tablet were said to be “80 percent likely” for release at the San Francisco event.