What do you call a disease with an unknown cure?

I am specifically trying to avoid "incurable" and its synonyms, as it precludes the possibility of a future medical breakthrough that would render its object preventable or curable.

That would render this category of words useless, since this can never be precluded.

It's ok to say incurable -- it's understood that there's an implicit "currently" riding with the word, since no disease can be intrinsically incurable.

I agree with @starwed's answer. But you can perhaps consider the following terms which may provide the nuance that you are looking for:

1. Remediless: Not having a remedy; not capable of being remedied.
2. Irremediable: impossible to cure or put right
3. Immedicable: unable to be healed or treated; incurable.

Even though they appear to be synonymous with incurable, I've added 2 and 3 simply for the sake of completeness. All three words suggest that there is no drug/remedy/medicine or treatment available for an illness or injury.

Although I think starwed comes very close to answering Sel, I'm not entirely certain that the essence of Sel's question has been truly addressed in all of the fascinating discussion that has gone on here. What Sel wants is a word that specifically states that the disease has no cure at this time, but also that it is likely to be cured at some future time.

In response, starwed points out that "incurable" does not preclude a future cure, and I think this is right, but if I am not mistaken, Sel wants something more. What seems to be wanted is a stronger implication within the desired word that although the disease does not have a cure, a cure is expected.

If I am correct about this, then I have to say to Sel, in my 36 years of experience in medicine, I have never encountered such a word. That doesn't prove such a word doesn't exist, but I'd bet quite a lot on its nonexistence.

I have seen this called a disease with no known cure.