A MacRumors forums member discovered last Thursday that the headset had been changed to a status of "discontinued" on the Apple Store.
The move is widely speculated as being house-cleaning related to Apple's June iPhone refresh. While it could simply be End-Of-Life (EOL) because Apple is leaving the Bluetooth business to others, many believe that it's a harbinger that a replacement is coming.
Since Apple announced support for A2DP (stereo Bluetooth) in iPhone OS 3.0, there's a good possibility that Apple's next headset will support it. I just hope that Apple keeps the iPhone Bluetooth Travel Cable, one of its best qualities:
This handy cable does double duty: It syncs and charges your iPhone or iPod, and it charges your iPhone Bluetooth Headset. Just plug it into a computer or an Apple USB Power Adapter.