WordPress is a collaborative effort by people from all over the world. Being an open-source platform (meaning that anybody can see and use the code which actually enables WordPress to press words), it is vital to have engaged and interested participants who will help to bring the next iteration to life.
One of the best ways to learn is by doing. And there is plenty that needs doing over at WordPress central. Everyone is invited, from experienced coders to those who are just learning PHP. And writers, too! (Somebody needs to make the documentation read like a Grisham novel.)
You can learn all of the many ways that you can help WordPress to continue to evolve by vistiting the Make WordPress page at make.WordPress.org.