Because buck has killed spitz before the beginning of chapters 4 and 5 his character can be said to have

completed his story arc
completed his character's development arc along a moral spectrum
never truly realized his potential
not yet completed his story arc and will not achieve the full arc until the end of the story

the swan might be a metaphor for our soul, which is ancient and timeless. the speaker wants to know where it's going and what it wants, what's the purpose in life. he asks our soul to follow him in knowing that god is us and the answer to the question "who am i" that was written on the wind of god's whim to know himself that blew over his being in the beginning of creation. and to connect to god consciously on the path to knowing him is the joy of loving him, like a bee that will grow and end our sorrows by ending desire. in that connection there is no doubt about god and existing forever.