I think it's a very real possibility. There's a tendency in people (including both scientists and non-scientists) to believe that whatever is now known about something like science and medicine (but also other areas) is all known, and there's little left to be learned. (The thinking is so often, "After all, look at the vast amount that is now known, particularly compared to what wasn't previously understood.")
I don't think we can go by comparing what was once known (at any given time in history) to all that is now known (and then think we're close to knowing everything at this point). I think we need to go by the hard-to-get-our-brain-around fact that answers and solutions tend to lie where only imaginations, better understanding, and determination can lead.
Over the course of my life, I've seen time and time again, instances in which scientists, the medical profession and/or other experts have operated under the belief that everything there was to understand about one thing or another was already understood; and that there was nothing left to question or figure out. Then, all of a sudden: "Oopsie. Guess what we discovered! All these years we've been thinking 'x', and now we see that there's 'y' to factor in."
I know I could be wrong, but I truly believe that a cure will be figured out.