Gizmodo saw a demo of Bluetooth over WiFi at the Mobile World Congress, and says the transfer speeds of this new technology were amazing. This new specification will be official in April, it's named alternate MAC/PHY and the good news is some phones may support it right now after applying a software update:
And unlike other technologies, it won't be in limbo for a while before reaching consumers. In fact, your phone may support it right now, according to Broadcom's Mukul Suth: Some of their current production chips already have this ability and they will only require a software upgrade to implement it.
The alternate MAC/PHY method is quite clever: The two devices discover each other and shake hands using Bluetooth (being cellphones, computers, or any other shiny thing supporting the standard). When you start any file transfer, the communication gets passed to the Wi-Fi hardware layer, which will transfer your data at 54mbps. Once the transfer is over, Wi-Fi is disconnected and the control passes again to Bluetooth.