Yes, I agree with Ben. Diseases do tend to evolve over time and with our environment, for example the causes of lots of diseases now are due to our lifestyle and are very different to those from 100 years ago. Things like viruses are also very good at evolving. As we and our environment evolve, so will the diseases we get. However, I think we will continue to develop cures and our understanding of diseases will be much greater, so the proportion of treatable diseases will be much higher.