There is the argument that the answer to this question 20 years ago was... 20 years. And since there is no cure NOW, which is 20 years later, than what reason do we have to believe that a cure will be found 20 years from TODAY?
But we have made quite a few advances and discoveries, which puts us quite a bit ahead of where we were 20 years ago, or even 5 years ago. Hell, we have discovered the link between male pattern baldness and DHT, and we have mapped out the genome, only within the past 5 years. So you can't compare the answer that you'll hear now to the answer that you would have gotten back then. I think these steps have put us higher on the learning curve, and that we really will have a cure to male pattern baldness within 5-7 years.
I hope so, anyway.