There's really not an answer to that question. Some improve and some don't. Some respond to speech therapy, some do not. Some find ways to cope with it, some don't. I can't speak for everyone here, but it does seem that many (but not all) adults see improvement as they age. And we can regress too. I've had bad YEARS where I was doing SO well and it's like my internal rhythm gets messed up again. I have to go back and practice and gain confidence all over again.