I placed a deposit on an 07 M3 coupe, but being I am getting it through Pentagaon Car Sales I will be paying a thousand or so under MSRP. But with your situation I would just contiue to shop around with other dealerships. With the car not being released for another year, I don't see why a dealership would not take your deposit money and not impose a markup. You can only assume they are expecting the next M3 to be a really hot item and are expecting to really screw over buyers when the car is released. Being your dropping money a year in advance the transaction is benefits both parties.
A car that doesnt even exist is already sold with little to no work
Option of investing the deposit you give them
Assured car will be available to you upon release.