As far as I know, koalas are currently listed as a “vulnerable” species. This means they are not in immediate danger of becoming extinct but they are still at risk. Like a lot of animals, the koala population is under threat due to loss of habitat from humans (it is predicted that up to 80% of natural koala habitat has already been destroyed). Increasing global temperatures are also increasing the likelihood of bushfires. Bushfires can not only kill koalas directly but can also destroy their food source for several weeks.
The quick answer is that koalas will probably be okay for the moment, but increasing human population growth and climate change without control could put them in more danger in the future.