"Johnny-come-lately" is an expression used to describe someone who is new to a particular situation or activity. However, there are several antonyms found for this phrase such as seasoned, veteran, experienced, long-timer, and old-timer. These antonyms depict a person who has been around for quite some time, and thus has a great deal of experience and expertise in their field. They are fast learners and possess a wealth of knowledge that newbies can learn from to excel in their respective fields. So, while a Johnny-come-lately is a newcomer, there are plenty of antonyms that describe an individual who is highly experienced and knowledgeable.