How long will the iphone 5s be supported with software updates?

The 5s has stopped getting updates. It can not be updated to iOS 13.

There is a non-zero probability that it might get a minor security fix at some point over the next few years, but that's extremely rare once a device stops getting major version updates.

The iPhone 5s lost software support with iOS 13, the last version of iOS that supported the iPhone 5s was iOS 12.4.2.