When the new regulations in Europe come into effect in 2023. Will DJI be sending a firmware downgrade limiting existing Mini 3 pro usage to 120 metres from controller?

No one knows, but I wouldn't put it past them.  

wait, they haven't already done that? /s

Maybe ask in the Mini 3 forum? This is the Air 2S forum.

Hello there. Good day and thank you for reaching out. Just a friendly reminder to always check local rules and regulations before flying your DJI Mini 3 Pro, as they may change over time and to avoid any unwanted incident. Thank you.

Thanks to the Stevo Super Mod to move this topic to the correct forum.

Another very good reason not to update stuff if all is working well. DJI would easily creep stuff like this into updates and not tell you

DJI need to remember that the U.K. is not in the EU

No. Enjoy flying, the future is never seen by some. "Don't worry be Happy".

I thought the EU had extended their transitional period seen as there are no C class drones on the market yet.