BMW released a major update of its iDrive systems in September 2008 (this was the first one with harddisk and internet access) starting with the facelifted 3series as far as I remember.
The 3series Coupe got a facelift earlier this year, which included again an updated iDrive version with new features, one of these e.g. music streaming over BT...

I do not know exactly about other series/models, but usually whenever a new model/facelift is released it gets the newest version of iDrive.

Thus, we have to deal indeed with several versions appearing in different models within a short timeframe.
But I don´t think the BT Stack / PBAB profile / expected vCard format differs too much from version to version, as this would cause to much trouble with all the mobile phones they have to support...