@ecrissey
The new Roku Ultra 4850 will still support all the older protocols a/b/g/n/ac and now ax.
You would of course need a new router only if you want to take advantage of the wifi6(ax) speeds and benefits. Otherwise, your wifi5(ac) router will still work with the Roku Ultra 4850 and can use n/ac on the 5ghz band.
As a general rule, any new protocol will be backwards compatible with the previous protocols. As long as you don't exclude the older protocols in a router (ie. setting "ax-only" rather than "ac/ax" in a wifi6 router) then both wifi5 and wifi6 clients can communicate with the router. In your particular case, the wifi5 router will simply recognize it's b/g/n/ac capabilty and operate as usual like it did with your previous Roku device.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102
