I am really excited about Bluetooth 4.0. Up until now Bluetooth has been quite a disappointment for anything other than simple wireless headset and subpar stereo headphones. I think that with Bluetooth 4.0 that will all change. The update to 4.0 will continue with the regular Bluetooth experience but add a high and low power mode. The low power mode could be useful for stuff as simple as remembering your car keys and sending messages to your watch with very little power draw. (Think sips instead of gulps) The high power/speed mode would improve upon the transfer speed bringing it beyond the 1mbps we usually see with regular Bluetooth.
The Bluetooth SIG announced that the Bluetooth 4.0 standard will be finalized in Q2 and will start showing up in devices by the end of the year. I am kind of excited to see what companies do with the new profiles! I am imagining a whole line of new accessories for my BlackBerry.