3Wagon, not to rain on your parade, but even when the adapter comes out, there still may be an issue. On older cars, some people have added iPods/MP3 players, etc. by hacking into the factory harness on the head unit, tapping into the tape deck output.
When they've done this, the output of the MP3 player or whatever comes out, but at a very low level. As such, some have added line-drivers (in-line signal amplifiers) to boost the signal to the headunit.
I hope that BMW has addressed this issue with '03 adapter, but we'll see.