Referencing a historically reliable source, AppleInsider claims that a future camera will take higher resolution stills in addition to video. The lack of a video camera has been a glaring omission since the beginning, and many users (including yours truly) have been waiting for its introduction.
Another rumor we're tracking is a boast of "faster internet speeds." Just what could that mean? AT&T's 4G network won't be ready for at least a year. It could refer to WiFi connectivity, as the current model has 802.11b/g (vs. n).
It's all conjecture, of course, so we'll have to wait and see. The iPhone 3G was announced on June 9th of 2008, and iPhone OS 3.0 is scheduled to be released this June. It wouldn't be a surprise to see the 3G phone drop in price while a new model takes the top slot at the same time.