You are right to an extent . The reason I am saying this is because BB customers are of upper middle class and are ready to pay for good service. If your target is to generate revenue then BB is still the best bet. Rest depends upon your idea. For Android and iOS they are the future specially Android.
All the best mate.
If you feed fish to a man you serve him for one day. BUt if you teach him to fish you serve him for his lifetime.