The estimates for Q4 can be nothing but good news for Apple, as Piper Jaffray analyst Gene Munster raised his assessment for iPhone sales from a little over 4 million to 5 million units. This would leave Apple with more than 2.5 million iPhones to sell before the end of the year, in order to reach their very optimistic objective of selling 10 million iPhones by the end of 2008.

We are almost a month away from finding out Apple’s quarterly results, but according to the most recent report by Piper, Apple had plenty of time to sell 5 million units, following the big announcement that it sold 1 million iPhone in the first weekend after launch.

Among the factors that may have contributed to bigger sales for Apple is of course the wider availability of the phone, compared to the moment iPhone first came on the market. Furthermore, despite some controversy regarding network and hardware problems, the Piper analyst believes that the company remains on track to reaching the 10 million goal.

Munster also remarked that, based on NPD sales data, Apple had a pretty good quarter, with sales going even higher than initial estimates, although the Macs and the iPods did a “poor” job compared to the iPhone, which despite all issues, seems to be gaining popularity.

It still remains unclear what happened to that incredible demand on the Asian market that raised the production of iPhones to 800,000 a week, which suggested Apple would reach the 10 million goal by the end of September.

Whether Apple slowed its pace, or the demand was actually not that high, we still don’t know. However that may be, Apple seems to remain on track, and the quarterly results they will announce next month will probably reflect the success of the iPhone.