For WTF/Kukkiwon taekwondo the black belt forms: koryo (virtueous man), keumgueng (diamond and mountain), taebaek (bright mountain), pyongwan (a vast plain), sipjin (life and longevity), jitae (struggle and aspiration), chonkwon (heaven), hanseu (water) seem to be paths towards Ilyeo (Buddhist enlightenment). There may be some incidental references to water, earth, mountain, and heaven as those are essential trigrams of the i-ching, but the path of the poomse suggests to use the gifts of the Earth to go beyond the struggle of man towards Buddhist enlightenment especially as the symbolic references of the latter forms are of softer elements and embracing of the spirit of Heaven and selflessness. So in a way they follow the course of change (e.g. I ching) You also have to remember that I Ching is a Chinese /Confucius philosophy and the Koreans have adopted some of these, but it seems that the taekwondo forms (specifically, the Kukkiwon standard ones) are less about I Ching than a path towards selflessness and enlightenment (other than change, in of itself).
The I Ching is a deep discussion of all changes in and around the Earth and can represent the boundless opportunities and chances that are here. It would be neat to see the forms try to encompass this vast philosophy, but I do not think the current set of black belt (or even taeguek or palgwe series) would yield as much meaning as the I Ching.