Originally Posted by
Scyclone
Trunks hair darkens as he gets older eventually to a variation of Bulmas Hair color (it is mostly a matter of color correction in the art side of things - think of it like kids with silver blonde hair darkening over time). This gets resolved in DB Super, where his hair is the appropriate color.
King Kai (and the others) chose to stay dead, to accompany Goku.
Android 17 put himself into a complete exile (away from everyone and everything) after he was brought back. Eventually he gets married and has kids. This gets covered in DB Super as well. He does, however, give his energy to the spirit bomb to defeat buu.