Check out this graphic with the ages that speech sounds should be developed.
Each child is different and will develop at their own rate. If a sound hasn’t been developed by the age shown they will most likely need help from a speech therapist to learn, develop, and generalize the sound. Most children will not learn the sound by themselves as they get older. As we get older we grow more set in our ways in more ways than one. It’s easier and faster to change speech sound errors at a younger age, before the sound should be mastered, or at that age.
If you have questions about sound development please send me an email at firstname.lastname@example.org.