There is no doubt that computer will HELP doing mathematics, and they are already helping. Computers are better in doing some jobs, humans are better in doing other jobs. I believe that there will always remain something in mathematics that only humans can do.
It is difficult to predict, of course what exactly computers will do better. 50 years ago it was widely believed that soon computers will translate text from one language to another, but playing chess well seemed more difficult for a computer. Now computers play chess better than humans, but their ability to translate is very limited. Try to translate a moderately difficult text with any program or with Google translate, and you will obtain garbage in most cases.