According to several posts on the hackint0sh forum, the chipset that will support the 3G iPhone will be the PMB8878 or better known as the S-GOLD3H.
The current version of the iPhone is powered by the S-GOLD2 chipset, so we might have found the chip that will power the next iPhone.
But maybe apple is planning to use another chipset, we will not know this until final release !
» iPhone 3G chipset found?

The following news just got posted on Macrumors.com.
Gartner analyst Ken Dulaney claims to have heard “from sources in Asia” that Apple has placed a 10 million unit order for 3G iPhones, according to an interview by the iPod Observer.
This order for 10 million 3G iPhones would reportedly be above and beyond the original 10 million Apple had planned to sell of the initial version of the iPhone in 2008.
» 3G iPhone coming in the next few months?