Before people start screaming and cancelling your reservation, ask yourselves how much you really use your sunroof in your past cars. Most people are like me and open it maybe a few times a year. They are known to be sources of leaks and wind noise and mechanical problems. Plus, I must point out that the MX also doesn't have a sunroof option because of the Falcon Wing Doors. It's just not possible to have the panoramic windshield and the FWD and put in a sunroof.
For those worried about having constant glass overhead, the special zinc coating on the glass reflects harsh light and UV and most of the heat so it hasn't been a problem in the MS or MX so should not be a problem for the M3.