Bluetooth 5.0 sadly doesn't improve the audio quality. Battery life and range are improved.
Does Bluetooth 5.0 really improve audio?
In short, no. But it one day could. Most of the improvements that come in Bluetooth 5.0 apply to Bluetooth Low Energy, which is used for things like fitness trackers, smart home devices, and so on. Headphones use Bluetooth Basic Data Rate/Enhanced Data Rate, also known as BR/EDR, which doesn’t really benefit from the improvements in Bluetooth 5.0.
In the end, Bluetooth 5.0 is an important update — just not for headphones. Hopefully, eventually, many of the improvements coming in Bluetooth 5.0 will apply to headphones, but for now when you’re buying a pair of headphones you don’t need to worry about buying a pair that uses Bluetooth 5.0.