The event may explain as well the “future product transition” that compelled Apple to forecast a nearly 5 percent drop in gross profit margin for the final quarter of the 2008 fiscal year. Apple offered few details of that transition, though CFO Peter Oppenheimer said during a July earnings call that it will involve “state-of-the-art new products that our competitors just aren’t going to be able to match.”

“One of the investments we make is to introduce new products that initially cost more because they deliver an entirely new level of value to the customer,” Apple COO Tim Cook said during the same call. “Then we ride the cost curves down with value engineering and volume manufacturing, leaving us far ahead of our competitors. We have some of these types of investments in front of us that I can’t discuss.”

Until Tuesday, Oct. 14, that is.

“Field checks confirm that shipments of new MacBooks have begun, with a sharp production ramp planned for September and an introduction planned for early October,” Gardner wrote. “The most distinctive features of the new MacBook appear to be a very thin aluminum casing, an LED-backlit display and an aggressive entry-level price point.”

Gardner expects Apple (AAPL) to introduce its fall notebook line “within weeks.” October 14, perhaps?