Basics
The K-19, K-20, and K-21 are fundamental designs. The basic ways of folding a piece of paper into an airplane aren't limitless, and these three plans may be among the best of the possible ways of doing it.
Each of these designs offers a nice range of dimensional adjustments and other variations that can achieve a range of appearances and flying characteristics in the individual finished plane. That's what makes them super-fun and maybe even educational.
I want to focus on these finer variations and am excited about the trigonometric analysis that I've only recently started applying to the designs.
I kind of hope I'm not blessed with thinking of any more fundamental original designs right away. I want to focus for now on optimizing and presenting the current ones as best I can and hope they really catch on with hobbyists the world over.
I want to maintain PaperAirplanes.net as an easy-to-remember site name for years to come where people can count on being able to learn and recall the designs.
Extras
The number of ways to fold a piece of paper into an airplane may not be limitless, but it could be fairly large. While pondering the question of just how large it is I'll probably think of some more.
Adaptation of the current designs to standard international and perhaps other paper sizes.
Try out different types of paper
More fins and flight testing
Usability improvements on the site as needed
Sales of accessories