Mandatory for now. Given enough time, I believe mankind will effectively cure all disease.
Not that you said we did, but many kind of think like that's the case, for hand wavy reasons, like "the sky is the limit", "human ingenuity is limitless", etc...
What are you even talking about? Humans have existed something like 200,000 years. In 500,000 years from now (or less), evolution will have changed us into something entirely different.
The better rebuttal is that currently it looks like we'll crash the planet's ecosystems and with them technological civilization within the next century or two, long before we've reached the point of curing all disease.
Species will evolve to thrive in the new ecosystem. Perhaps that will be a subset of humans evolving into something else, perhaps not. But life won’t disappear because we raise global temperatures.