D-Link has stated that new gen routers, access points and range extenders will connect using WPA2 (AES) by default when the mixed security (WPA/WPA2) is enabled. The iOS 14 message will be displayed if it detects that the router/ap/extender has mixed security enabled but will still connect using WPA2 AES.
Some devices will get firmware upgrades to allow you to select WPA2 Only (and WPA3 only if the chipset supports it) in the future. No list or time table available.