iPhone 3G uses Bluetooth 2.0 + EDR, but it seems like the folks behind the BT standard are ready to release the next big version, coincidentally sharing the same 3.0 version number as the next iPhone firmware update, coming this summer.
There's been no word on Apple adopting Bluetooth 3.0 for iPhone OS 3.0 or the next generation iPhone hardware expected to be previewed at WWDC in June, but according to BGR, it will be landing on April 21st and will enable:
Ultra-wideband (UWB) wireless technology to achieve transfer speeds of up to 480Mbps. No, seriously. Higher transfer speeds are actually achieved by enabling 802.11 standards when heavy lifting is involved and then switching back to an older, slower standard when big transfers are completed.
Of course, Apple's track record when it comes to BT is not good, so there's no saying whether or not they'll make the jump to Bluetooth 3.0 now... or wait for 2015 to roll around...