Oh goodness. Well, I have successfully treated severe fin rot with just salt baths and betta fix. Go to the Salt bath thread, or get some heavy duty meds from your local pet store. Like, Ampicillin, Maryicin (don't know how to spell that).
If you don't care for your fish and do what you can, it could drop dead any second, or five days from now, or even weeks. Don't concern yourself with WHEN the fish will die. Just do what you can to help your fish, and do it soon.
Right now I put him in another tank. I cleaned his other tank,took ALL the water out, and now I'm cooking the gravel because I heard that's how you get rid of the bacteria in it. I'm planning to fill his tank again and then going to the store and buying some medicine. Any more suggestions. BTW he seems more calm and relaxed in the another tank so maybe the other water was contaminated. And also I had 2 catfish there that my dad brought from some salty water but I took those out and gave them to my uncle. I think those were the cause of A) Ick to my fish, and B) Getting my fish sick again with rotten fins.