Despite WiFi 6 being made official, it will still take some time for it to finish baking in the hands of early adopters. You may wish to wait on that basis alone, as well as for prices to come down.
That said, it also depends on what you do with your network. One of the new features in 6 is better handling of network congestion, and well as better speed, so if there are a lot of devices in use, they can take advantage. Battery life improvement is another touted feature.
And don't forget, routers are computers in and of themselves, with processors, memory and an OS, and a more modern router can still be an improvement given the same internet connection, especially if it's also tasked to handle things like running a VPN.
A classic like the WRT54G used to be the state of the art, but it's no longer 2002, and technology has advanced.
It wouldn't be unwise to wait, but the benefits can't be dismissed either. It will just take some time for adoption to spread and prices to come down.