Gene Munster of Piper Jaffray is at it again. This time he's proffered up his predictions for Apple's fourth quarter sales. He says Apple is primed to sell 5 million iPhones between now and the end of the year, and that the iPhone will represent a "meaningful percentage" of Apple's revenue.Five million? Really?

According to Business Week, Apple sold 2.4 million iPhones in the first half of 2008. That's before the 3G iPhone arrived. Apple reported that it sold 1 million 3G iPhones the first weekend the device was available. But Apple hasn't reported its July - September earnings yet, so we don't know how many iPhones it has really sold during the third quarter.

Jaffray's Munster has taken a close look at retail data and has raised all his estimates for Apple sales for the rest of the year. Not only will Apple sell more computers and iPods than it has in the past, but Munster predicts a healthy 5 million iPhones will sell during the key holiday season.

Where does that put Apple it terms of its goal to sell 10 million iPhones during 2008? Pretty darned close. If we take the first half of '08 numbers from Business Week and add in Munster's 5 million, that takes us to 7.4 million total. That figure leaves out all of the 3Q '08 sales numbers, though. What do you think, has Apple sold 2.6 million iPhones between July 1 and Sept. 30? I would bet that it has, meaning Apple is probably on target to reach its 10 million iPhone goal.

The bigger picture is that Munster says for the first time that the iPhone will become a significant part of Apple's overall revenue in 2008. He pegs the number at 21%, versus 4% for the second quarter of this year. That's a pretty darned big percentage. One out of every five dollars that Apple earns will come from iPhone sales.

We should have a clearer picture once Apple reports its third quarter earnings, which should be in a few weeks.