Since there's no hope that I'd actually release anything within five years or more, I don't think I'll spend too much time worrying about frame rates or memory optimization or whatever -- who knows what graphics hardware will be like five years from now?
I imagine nothing will come of it, but making planets looks like too much fun, though Ysaneya's incredible work will be hard to follow. So anyway I got a book on OpenGL and coded up a first little test. It doesn't look much like a planet yet!