Eh, it’s an issue and it may get worse than it is today, but it will never be as big of a deal as cancer.
The nightmare scenario of antibiotics one day becoming useless because all bacteria are resistant to them is just not realistic. First of all, antibiotics aren’t new. Many of them weren’t invented, they were discovered. Which means they existed in fungi or other bacteria for millions of years and were used to fight unwanted bacteria. Penicillin is named after the Penicillium mold, for example.
Antibiotic resistance is a survival strategy for bacteria that are under a lot of stress from antibiotics. This happens in hospitals, nursing homes or farms where antibiotics are used en masse. In these places, resistant bacteria have a clear advantage over normal ones, so they can quickly replicate without much competition. But as soon as you take away the antibiotics, that advantage disappears and suddenly they have to compete with the normal bacteria again. Plus, maintaining the antibiotic resistance is effort. They have to produce special proteins or change the ones they normally use, which can make them less efficient.
So most likely, antibiotic resistance will continue to be a problem mainly in places where lots of antibiotics are used all the time. As soon as we reduce usage, resistance will go down. There are certain antibiotics that haven’t been used in decades due to side effects, such as Colistin, which can now be used to treat multi-drug-resistant bacteria because they haven’t been exposed to it for so long. Other antibiotics like quinolones are currently falling out of favor, so they may be the magic bullet of the future.
One more aspect is that antibiotics don’t make a lot of money for pharmaceutical companies, because they’re usually only taken for days or a few weeks, while other drugs such as heart medication are taken lifelong. That’s why there’s not a lot of (private) money going into antibiotic research. But if the situation gets bad enough, this may change and it will likely mean that a lot more new antibiotics are developed.