There is no definitive answer to this question as Wi-Fi 6 networks are still in development and may not work as well on older Wi-Fi 5 networks. However, if you have a Wi-Fi 6 device and are using a Wi-Fi 5 network, it is likely that you will be able to connect and use the device.
Don’t Worry, Your Devices Are Backward Compatible
Wi-Fi standards are, thankfully, backward compatible across generations. Whether you have a Wi-Fi 6 router and a Wi-Fi 6 device, a Wi-Fi 5 device and a Wi-Fi 4 router, or any number of permutations of the Wi-Fi standards from the last twenty years or so, your newer device can connect to your older Wi-Fi router.
That means whether you’re connecting your new iPhone that supports Wi-Fi 6 to a Wi-Fi 5 router you haven’t upgraded yet or to the very dusty old ISP-supplied Wi-Fi 4 router at your parent’s house, your phone will negotiate a connection to the router using the appropriate Wi-Fi technology.
You Won’t Get Wi-Fi 6’s Improvements
You can use new devices on old routers, so upgrading your phone doesn’t automatically mean a forced Wi-Fi router upgrade. But there is a downside to using devices that support new Wi-Fi tech on older network hardware.
While your new phone or other devices will happily switch to an older Wi-Fi version to get you a connection, it’s a downgrade from what your device is capable of.
You won’t get the maximum speeds the newer version of Wi-Fi could afford, nor will you get any of the Wi-Fi 6 improvements like better device battery life, less wireless congestion, and better performance in a home with many devices. (You do get those improvements with Wi-Fi 6 devices connected to the router, just not with the Wi-Fi 5 devices.)
So while you don’t need to upgrade your router to Wi-Fi 6, it’s not a bad idea to seriously consider it at this point. More and more devices support Wi-Fi 6, and even if the bulk of your devices are still Wi-Fi 5, upgrading your router improves the Wi-Fi experience network-wide.