Look, never is a long time. Who knows what will be possible in 500 years? But I think it’s unlikely that we will ever be able to claim that every cancer — covering a truly massive number of individual disorders — can be cured.
I do hope to be proven wrong, but I think this is one area where there is some very justifiable cynicism. Even curing a single mutation of a single type of cancer is an enormous, decades-long endeavor.