I looked at the pics of the new X5M that someone posted earlier in the week and the M steering wheel had a button for heating. Also on the M5 they are offering steering wheel heating ... so it might have it now.

I must confess, the M steering wheel in my 2008 M3 is the best steering wheel I've ever owned. I will really miss it. I hope that I will be able to retrofit this new M sport pack steering wheel to my very non sporty X5 35d !