Personally I think it is about marketing. If the cars had everything today, what would they upgrade tomorrow? The 5 got the new iDrive but not the upgraded power. The 6 got the upgraded power, but not the iDrive. These are real world enhancements and they drive customers to the showrooms. Just kind of sucks if you are an enthusiast. Just ask the guy wo picked up an 06 550 in Dec of 2005 only to have the 07s come out ( unexpectedly) in March of 06.
2017 M2, LBB 6sp w/exec
2011 1M, Black loaded sans sat radio