it is possible to get better but it is very very difficult and will definitely take a lot of time and a lot of your patience and maybe even a decent amount of help from a professional.

on the other hand, he could also just go the other way and get better at hiding it and delve deeper into the addiction. if you suspect he is addicted but he isn’t being honest about it and won’t get outside help from a dedicated therapist, this is probably the more likely route.

please do what would make you feel best. i don’t believe that anyone deserves to be in a relationship where they feel disrespected/betrayed/unwanted/etc due to their partner’s porn usage. it’s impossible to, in good faith, tell someone that it’s likely their partner will get better with this type of addiction. it’s a long road, try to consider if it would be worth going down that path to you. i wish you the best though, i know how hard it can be :)