Rumors about an upcoming Apple event taking place in September which will introduce a new series of iPod and MacBook models were recently released by Piper Jaffray, a U.S. middle-market investment banking company.

The firm believes that Apple will stick to the same strategy embraced for the past three years and upgrade some of its top-selling models at the end of summer. One of the clearest signs about Apple’s intentions is the bulletin sent to its resellers, which invited all the interested parties to stack up on iPods, 13-inch MacBooks and 15-inch MacBooks Pros, as the production will be slowly ramping down over the next few weeks and these products will be a lot harder to order.

"We note that the MacBook has had the same design since its launch over two years ago, and the MacBook Pro has had essentially the same design since its launch over 2.5 years ago, which was very similar in design to the PowerBook G4 released over 5.5 years ago," Piper Jaffray wrote in a note to the interested clients.

A similar marketing strategy was chosen before the launch of the new iPhone 3G, with the original 2.5G iPhone gradually disappearing off the shelves several weeks before the big launch.

The re-edition of the iPod nano might include a tall-screened version and the iPod touch might also be in the works for a make-over.

Keeping to itself as usual, Apple did not release any specifications about the new features and there are very few details about the possible upcoming changes, most of which are only assumptions.