According to TG Daily sources, the 3G iPhone will indeed launch at WWDC 2008, which will be held from 6th June at San Francisco.

Similar to the current iPhone range, the new 3G iPhone will be available in 8GB ($399), 16GB ($499) and a rumor 32GB ($599) version. The rumor also include a 2.5mm thinner body, although the battery wil be still a non-removable battery.

The phone casing will be also tuned a bit, check out the new casing rumor below

http://www.slashphone.com/rumor-is-this-the-back-of-3g-iphone-06104

Source [TG Daily]