Bluetooth protocols and radio frequencies have not changed. Basic pairing functions should always work. Once paired different functions may or may not be supported but basic hands free should always work.
BMW have about 9 generations of the Bluetooth module in the X5!!! But mostly they are improved antenna more reliable connection etc.
Something about the iphone can cause the pairing to fail if you have too many text messages saved. It sees the car but never offers the code input box.
I had to delete all saved text messages and after that restarted the pairing. Worked right away after that.
In my 2006 I get my address book , onscreen feedback of phone numbers incoming and outgoing on both the nav screen and the dash board.
Works great.

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I've got a 4s but I paired a friends 5 just fine.