The truth is, there's no way of knowing, my testicles did get bigger in my early to mid 20s, i was already pretty mature by 19, and Ive read many places that your shaft changes bit up to 24 years of age, which probably is the truth, as most scientifically empirical data in the medical field isn't always "accurate", docs will tell you some things you cant heal from when you totally can, and honestly most boys mature a little bit on into the 20s, but its observable, all of the young college kids near where i live in Texas, the boys still look like they are maturing, and they are 19 or 20.....if your honest with yourself you can see them in a few years and they are either a little bit taller or they visibly changed. So honestly the top out age for male growth is about 25 ish,
A Doctors answer will be no, but for every few doctors that so no, youll find one that will be upfront with you and say that there's no way of determining that for anyone because most people mature slowly into there 20s, and yes that includes the penis, and testes. I wouldn't expect to be hung like a horse by 30 though keep in mind.