Well, after a billion years the sun will be too hot for life on Earth to survive anyway, so it seems a little pointless to worry about orbit destabilization at

Well, after a billion years the sun will be too hot for life on Earth to survive anyway, so it seems a little pointless to worry about orbit destabilization at that point; if we're somehow still around, we'll have to have moved off-planet anyway. That or taken control of the planet's orbit (to move it away from the sun), in which case we probably have the tools to handle the problem regardless.