BMW always believes in structural rigidity being a benefit to the response of a car. For that reason alone the only BMW models that will see the removal of a B-Pillar is Roadsters and Cabrio variants only.
every BMW Sedan , Coupe etc will always feature a B-Pillar it's what makes a BMW , handle like a BMW and be a BMW.
Although the E31 8er Coupe lacked a B-Pillar, many feel it contributed to the lacklustre handling of that car.
So much that Wolfgang Reitzle wanted the car re-engineered to accomodate a B-Pillar as the prototype M8 used a B-Pillar and completely transformed the car. The early nineties recession killed the strategy to do this.